Copyright Page

Chapter 1. CEF Overview

Finding Feature Information

Information About CEF

Cisco Platform Support for Central CEF and dCEF

Cisco Express Forwarding Benefits

Media Supported by CEF

Main Components of CEF

FIB Overview

CEF FIB and Load Balancing

CEF Adjacency Tables Overview

Adjacency Discovery

Adjacency Types That Require Special Handling

Unresolved Adjacency

Central CEF Mode Operation

Distributed CEF Mode Operation

CEF Features Enabled by Default

CEF Distributed Tunnel Switching

CEF-Switched Multipoint GRE Tunnels

Links for the CEF Features

How to Configure CEF

Configuration Examples for CEF

Where to Go Next

Additional References

Feature Information for CEF

Glossary

Chapter 2. Configuring Basic Cisco Express Forwarding

Finding Feature Information

Prerequisites for Cisco Express Forwarding

Restrictions for Cisco Express Forwarding

Information About Cisco Express Forwarding

Cisco Platform Support for CEF and dCEF

Cisco Express Forwarding Benefits

Main Components for CEF Operation

CEF Operation Modes Central and Distributed

Central Cisco Express Forwarding Mode Operation

Distributed Cisco Express Forwarding Mode Operation

How to Configure Basic Cisco Express Forwarding

How to Verify Basic Cisco Express Forwarding

Determining How the Router Is Configured

What to Do Next

Verifying Cisco Express Forwarding Operation

Verifying That Cisco Express Forwarding Switching Is Enabled

Locating the Prefix in a Forwarding Table on the RP

Finding the Cisco Express Forwarding Output Information

Verifying the Adjacency or Next-Hop Information

Verifying Distributed Cisco Express Forwarding Operation

Cisco Express Forwarding Command Syntax on Line Cards

Verifying That dCEF Switching Is Enabled

Locating the Prefix in a Forwarding Table on a Line Card

Finding the Distributed Cisco Express Forwarding Output Information

Verifying the Adjacency or Next-Hop Information on a Line Card

Interpreting Cisco Express Forwarding Command Output

Verifying That CEF Information Looks As Expected

Interpreting MPLS Information in CEF Output

Configuration Examples for Basic CEF

Where to Go Next

Additional References

Feature Information for Basic CEF

Glossary

Chapter 3. Enabling or Disabling CEF or dCEF

Finding Feature Information

Prerequisites for Enabling or Disabling CEF or dCEF

Restrictions for Enabling or Disabling CEF or dCEF

Information About Enabling or Disabling CEF or dCEF

Cisco Platform Support for Central CEF and dCEF

When to Enable or Disable Central CEF on a Router

When to Enable dCEF on a Line Card

When to Enable or Disable CEF on an Interface

How to Enable or Disable Central CEF or dCEF

Enabling or Disabling CEF or dCEF on a Router

Enabling or Disabling CEF or dCEF on an Interface

Configuration Examples for Central CEF or dCEF

Example Enabling or Disabling CEF or dCEF on a Router

Example Enabling or Disabling Central CEF or dCEF on an Interface

Additional References

Feature Information for Enabling or Disabling CEF or dCEF

Glossary

Chapter 4. Configuring a Load-Balancing Scheme

Finding Feature Information

Prerequisites for a Load-Balancing Scheme

Restrictions for a Load-Balancing Scheme

Information About a Load-Balancing Scheme

Cisco Platform Support for Central CEF and dCEF

CEF Load-Balancing Overview

Per-Destination Load Balancing

Per-Packet Load Balancing

Load-Balancing Algorithms

GTP-U TEID-Based ECMP Load-Balancing Algorithm for Cisco IOS XE Software

Restrictions for GTP-U TEID-Based ECMP Load-Balancing Algorithm

Enabling the GTP-U TEID Load-Balancing Algorithm

How to Configure a Load-Balancing Scheme

Enabling or Disabling Per-Destination Load Balancing

Configuring Per-Packet Load Balancing

Selecting a Tunnel Load-Balancing Algorithm

Selecting an Include-Ports Layer 4 Load-Balancing Algorithm

Configuration Examples for a Load-Balancing Scheme

Example Enabling or Disabling Per-Destination Load Balancing

Example Configuring Per-Packet Load Balancing

Example Selecting a Tunnel Load-Balancing Algorithm

Example Selecting an Include-Ports Layer 4 Load-Balancing Algorithm

Additional References

Feature Information for a Load-Balancing Scheme

Glossary

Chapter 5. Configuring Epochs

Finding Feature Information

Prerequisites for Epochs for CEF Tables

Information About About Epochs for CEF Tables

Cisco Platform Support for Central CEF and dCEF

Nonstop Forwarding Enhanced FIB Refresh

Epoch Numbering for CEF FIB and Adjacency Tables

Epoch Synchronization Between the RP and Line Cards

Epoch Numbering for Routers That Support HA

When to Refresh the CEF or Adjacency Tables

How to Configure Epochs

Incrementing the Epoch Number of the Adjacency Table

Incrementing the Epoch Number of One or All CEF Tables

Verifying Epoch Information

Configuration Examples for Epochs

Example Incrementing the Epoch Number of the Adjacency Table

Example Incrementing the Epoch Number of One or All CEF Tables

Additional References

Feature Information for Configuring Epochs

Glossary

Chapter 6. Configuring CEF Consistency Checkers

Finding Feature Information

Prerequisites for CEF Consistency Checkers

Restrictions for CEF Consistency Checkers

Information About CEF Consistency Checkers

Cisco Platform Support for CEF and dCEF

CEF Consistency Checker Types

How to Configure CEF Consistency Checkers

Enabling CEF Consistency Checkers

Displaying and Clearing Table Inconsistencies

Configuration Examples for CEF Consistency Checkers

Example Enabling CEF Consistency Checkers

Additional References

Feature Information for CEF Consistency Checkers

Glossary

Chapter 7. Configuring CEF Network Accounting

Finding Feature Information

Prerequisites for CEF Network Accounting

Restrictions for CEF Network Accounting

Information About CEF Network Accounting

Cisco Platform Support for Central CEF and dCEF

Traffic Matrix Statistics

TMS and CEF Nonrecursive Accounting

How Backbone Routers Collect TMS

TMS Viewing Options

TMS Displayed with the NDA Display Module

Nonrecursive Accounting Information Displayed

Statistics in the timestats File

Statistics in the tmsasinfo File

How to Configure CEF Network Accounting

Configuring CEF Network Accounting

Enabling a Backbone Router to Collect TMS

Using the CLI to Enable a Backbone Router to Collect TMS

Enabling the NDA to Collect TMS on a Backbone Router

Interpreting the tmstats File

Viewing Information in the tmsasinfo File

Verifying CEF Network Accounting Information

Configuration Examples for CEF Network Accounting

Example Configuring CEF Network Accounting

Example Enabling a Backbone Router to Collect TMS Data

Example IP CEF Nonrecursive Accounting

Example Interpreting the tmstats_ascii File

Additional References

Feature Information for CEF Network Accounting

Glossary

Chapter 8. Customizing the Display of Recorded CEF Events

Finding Feature Information

Prerequisites for the Display of Recorded CEF Events

Restrictions for the Display of Recorded CEF Events

Information About the Display of Recorded CEF Events

Cisco Platform Support for Central CEF and dCEF

CEF Event Log Overview

How to Customize the Display of Recorded CEF Events

Customizing CEF Event Logging

Displaying CEF Event-Log Information

Configuration Examples for the Display of Recorded CEF Events

Example Customizing CEF Event Logging

Additional References

Feature Information for the Display of Recorded CEF Events

Glossary

Chapter 9. Customizing the Display of CEF Event Trace Messages

Finding Feature Information

Prerequisites for the Display of CEF Event Trace Messages

Restrictions for the Display of CEF Event Trace Messages

Information About the Display of CEF Event Trace Messages

Cisco Platform Support for Central CEF and dCEF

Overview of CEF Event Trace Function

CEF Event Tracing Defaults and Options

CEF Event Tracing for IPv4 Events

CEF Event Tracing for IPv6 Events

How to Customize the Display of CEF Event Trace Messages

Customizing CEF Event Tracing

Customizing CEF Event Tracing for IPv4 Events

Customizing CEF Event Tracing for IPv6 Events

Displaying CEF Event Trace Information

Configuration Examples for the Display of CEF Event Trace Messages

Example Customizing CEF Event Tracing

Example Customizing CEF Event Tracing for IPv4 Events

Example Customizing CEF Event Tracing for IPv6 Events

Additional References

Feature Information for the Display of CEF Event Trace Messages

Glossary

Chapter 10. SNMP CEF-MIB Support

Finding Feature Information

Prerequisites for SNMP CEF-MIB Support

Information About SNMP CEF-MIB Support

CEF Functional Overview

Benefits of CISCO-CEF-MIB

Information Managed by the CISCO-CEF-MIB

CISCO-CEF-MIB Object Groups

CISCO-CEF-MIB Tables

Operations Available Through the CISCO-CEF-MIB

CISCO-CEF-MIB Notifications

How to Configure SNMP CEF-MIB Support

Configuring the Router to Use SNMP

Configuring a Host to Receive Notifications

Configuring SNMP Notifications with the CLI

Configuring SNMP Notifications with SNMP Commands

Configuring the Throttling Interval with the CLI

Configuring the Throttling Interval using SNMP Commands

Configuration Examples for SNMP CEF-MIB Support

Example Configuring a Host to Receive Notifications

Example Configuring SNMP Notifications

Example Configuring the Throttling Interval

Additional References

Feature Information for SNMP CEF-MIB Support

Glossary

Chapter 11. Cisco Express Forwarding Command Changes

Finding Feature Information

Information About Command Changes

Deleted Commands

Replaced Commands

Additional References

Feature Information for Cisco Express Forwarding Command Changes

Chapter 12. CEF Enhancements

Finding Feature Information

Information About CEF

Introduction of CEF Enhancements

CEF Enhancements Described

Removal of Support for IPv4 Fast Switching

CEF Command Changes

CEF show Command Output Changes

show ip cef summary

show ipv6 cef summary

show ip cef internal

show ipv6 cef internal

show ip cef detail

show ipv6 cef detail

show ip cef internal

show ipv6 cef internal

show ip cef

show ip cef exact-route detail

show ip cef exact-route

show ip cef adjacency

show adjacency summary

show adjacency detail

show adjacency internal

show cef state

show cef timers

show ip cef epoch

show ipv6 cef epoch

show ip cef unresolved detail

show ipv6 cef unresolved detail

show ipv6 cef non-recursive

New Commands for the CEF Feature

show adjacency link

show adjacency

show adjacency detail

show cef tree

test cef table consistency detail

Unchanged CEF show Commands

Additional References

Feature Information for CEF Enhancements

Glossary

Chapter 13. IPv6 CEF-Switched Tunnels

Finding Feature Information

Information About IPv6 CEF-Switched Tunnels

IPv6 Manually Configured Tunnels

Additional References

Feature Information for IPv6 CEF-Switched Tunnels

THE SPECIFICATIONS AND INFORMATION REGARDING THE PRODUCTS IN THIS MANUAL ARE SUBJECT TO CHANGE WITHOUT NOTICE. ALL STATEMENTS, INFORMATION, AND RECOMMENDATIONS IN THIS MANUAL ARE BELIEVED TO BE ACCURATE BUT ARE PRESENTED WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED. USERS MUST TAKE FULL RESPONSIBILITY FOR THEIR APPLICATION OF ANY PRODUCTS.

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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: Click Here . Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R)

Chapter 1. CEF Overview

This module contains an overview of the Cisco Express Forwarding feature. Cisco Express Forwarding is an advanced Layer 3 IP switching technology. It optimizes network performance and scalability for all kinds of networks: those that carry small amounts of traffic and those that carry large amounts of traffic in complex patterns, such as the Internet and networks characterized by intensive web-based applications or interactive sessions.

- Finding Feature Information

- Information About CEF

- How to Configure CEF

- Configuration Examples for CEF

- Where to Go Next

- Additional References

- Feature Information for CEF

- Glossary

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to Click Here . An account on Cisco.com is not required.

Information About CEF

- Cisco Platform Support for Central CEF and dCEF

- Cisco Express Forwarding Benefits

- Media Supported by CEF

- Main Components of CEF

- FIB Overview

- CEF Adjacency Tables Overview

- Central CEF Mode Operation

- Distributed CEF Mode Operation

- CEF Features Enabled by Default

- Links for the CEF Features

Cisco Platform Support for Central CEF and dCEF

Cisco Express Forwarding is enabled by default on most Cisco platforms running Cisco IOS software Release12.0 or later. When Cisco Express Forwarding is enabled on a router, the Route Processor (RP) performs the express forwarding.

To find out if Cisco Express Forwarding is enabled on your platform, enter the show ip cefcommand. If Cisco Express Forwarding is enabled, you receive output that looks like this:

Router# show ip cef
Prefix              Next Hop            Interface
[...]
10.2.61.8/24        192.168.100.1       FastEthernet1/0/0
192.168.101.1       FastEthernet6/1
[...]

If Cisco Express Forwarding is not enabled on your platform, the output for the show ip cefcommand looks like this:

Router# show ip cef
%CEF not running

Distributed Cisco Express Forwarding is enabled by default on the Catalyst 6500 series switch, the Cisco 7500 series router, and the Cisco 12000 Series Internet Router. When distributed Cisco Express Forwarding is enabled on your platform, the line cards perform the express forwarding.

If Cisco Express Forwarding is not enabled on your platform, use the ip cefcommand to enable (central) Cisco Express Forwarding or the ip cef distributed command to enable distributed Cisco Express Forwarding.

Cisco Express Forwarding Benefits

- Improved performance--Cisco Express Forwarding is less CPU-intensive than fast switching route caching. As a result, more CPU processing power can be dedicated to Layer 3 services such as quality of service (QoS) and encryption.

- Scalability--Cisco Express Forwarding offers full switching capacity at each line card when distributed Cisco Express Forwarding mode is active. Distributed Cisco Express Forwarding is a distributed switching mechanism that scales linearly with the number of interface cards and the bandwidth installed in the router.

- Resilience--Cisco Express Forwarding offers an unprecedented level of switching consistency and stability in large dynamic networks. In dynamic networks, fast-switched cache entries are frequently invalidated by routing changes. These changes can cause traffic to be process-switched through use of the routing table, rather than fast switched through use of the route cache. Because the forwarding information base (FIB) lookup table contains all known routes that exist in the routing table, it eliminates the need for route cache maintenance and the steps involved with fast-switch or process-switch forwarding. Cisco Express Forwarding can switch traffic more efficiently than typical demand caching schemes.

You can use Cisco Express Forwarding in any part of a network. For example, the figure below shows Cisco Express Forwarding being run on routers at aggregation points at the core of a network where traffic levels are high and performance is critical.

Cisco Express Forwarding Example

Cisco Express Forwarding in platforms at the network core provides the performance and scalability that networks need to respond to continued growth and steadily increasing network traffic. Cisco Express Forwarding is a distributed switching mechanism that scales linearly with the number of interface cards and the bandwidth installed in the router.

Media Supported by CEF

Cisco Express Forwarding supports the following media:

- ATM/AAL5snap, ATM/AAL5mux, and ATM/AAL5nlpid

- Ethernet

- FDDI

- Frame Relay

- High-Level Data Link Control (HDLC)

- PPP

- Spatial Reuse Protocol (SRP)

- Token Ring

- Tunnels

Main Components of CEF

Information conventionally stored in a route cache is stored in several data structures for Cisco Express Forwarding switching. The data structures provide optimized lookup for efficient packet forwarding. The two main components of Cisco Express Forwarding operation are the forwarding information base (FIB) and the adjacency tables.

The FIB is conceptually similar to a routing table or information base. A router uses this lookup table to make destination-based switching decisions during Cisco Express Forwarding operation. The FIB is updated when changes occur in the network and contains all routes known at the time. For more information, see the FIB Overview section.

Adjacency tables maintain Layer 2 next-hop addresses for all FIB entries. For more information, see the CEF Adjacency Tables Overview section.

This separation of the reachability information (in the Cisco Express Forwarding table) and the forwarding information (in the adjacency table), provides a number of benefits:

- The adjacency table can be built separately from the Cisco Express Forwarding table, allowing both to be built without any packets being process-switched.

- The MAC header rewrite used to forward a packet is not stored in cache entries, so changes in a MAC header rewrite string do not require validation of cache entries.

FIB Overview

Cisco Express Forwarding uses a forwarding information base (FIB) to make IP destination prefix-based switching decisions.

The FIB contains the prefixes from the IP routing table structured in a way that is optimized for forwarding. When routing or topology changes occur in the network, the IP routing table is updated, and those changes are reflected in the FIB. The FIB maintains next-hop address information based on the information in the IP routing table.

Because there is a one-to-one correlation between FIB entries and routing table entries, the FIB contains all known routes and eliminates the need for the route cache maintenance that is associated with switching paths such as those used in fast switching and optimum switching.

- CEF FIB and Load Balancing

CEF FIB and Load Balancing

Several paths can lead to a destination prefix. This occurs, for example, when a router is configured for simultaneous load balancing and redundancy. For each resolved path, the FIB contains a pointer for the adjacency corresponding to the next hop interface for that path.

CEF Adjacency Tables Overview

A node is said to be adjacent to another node if the node can be reached with a single hop across a link layer (Layer 2). Cisco Express Forwarding stores forwarding information (outbound interface and MAC header rewrite) for adjacent nodes in a data structure called the adjacency table. Cisco Express Forwarding uses adjacency tables to prepend Layer 2 addressing information to packets. The adjacency tables maintain Layer 2 next-hop addresses for all FIB entries.

The following sections provide additional information about adjacencies:

- Adjacency Discovery

- Adjacency Types That Require Special Handling

- Unresolved Adjacency

Adjacency Discovery

Each adjacency table is populated as adjacencies are discovered. Adjacencies are added to the table through indirect manual configuration or dynamically--discovered through a mechanism like Address Resolution Protocol (ARP). Adjacencies can also be added through the use of a routing protocol, such as Border Gateway Protocol (BGP) or Open Shortest Path First (OSPF), which forms neighbor relationships. Each time an adjacency entry is created, a link-layer header for that adjacent node is computed and stored in the adjacency table.

The adjacency information is subsequently used for encapsulation during Cisco Express Forwarding switching of packets.

Adjacency Types That Require Special Handling

In addition to adjacencies associated with next-hop interfaces (host-route adjacencies), other types of adjacencies are used to expedite switching when certain exception conditions exist. Prefixes requiring exception processing or special handling are cached with one of the special adjacencies listed in the table below.

Adjacency Types That Require Special Handling

Packets of This Adjacency Type

Receive This Processing

Null adjacency

Packets destined for a Null0 interface are dropped. Null adjacency can be used as an effective form of access filtering.

Glean adjacency

When a device is connected to a multiaccess medium, the FIB table on the device maintains a prefix for the subnet rather than for the individual host prefixes. The subnet prefix points to a glean adjacency. A glean adjacency entry indicates that a particular next hop should be directly connected, but there is no MAC header rewrite information available. When the device needs to forward packets to a specific host on a subnet, Cisco Express Forwarding requests an ARP entry for the specific prefix, ARP sends the MAC address, and the adjacency entry for the host is built.

Punt adjacency

The device forwards packets requiring special handling or packets sent by features not yet supported in CEF switching paths to the next higher switching level for handling.

Discard adjacency

The device discards the packets.

Drop adjacency

The device drops the packets.

Unresolved Adjacency

When a link-layer header is prepended to a packet, the FIB requires the prepended header to point to an adjacency corresponding to the next hop. If an adjacency was created by the FIB and not discovered through a mechanism such as ARP, the Layer 2 addressing information is not known and the adjacency is considered incomplete or unresolved. Once the Layer 2 information is known, the packet is forwarded to the RP, and the adjacency is determined through ARP. Thus, the adjacency is resolved.

Central CEF Mode Operation

You can use central Cisco Express Forwarding mode when line cards are not available for Cisco Express Forwarding switching, when you need to use features not compatible with distributed Cisco Express Forwarding switching, or when you are running on a nondistributed platform. When central Cisco Express Forwarding mode is enabled, the Cisco Express Forwarding FIB and adjacency tables reside on the RP, and the RP performs the express forwarding.

The figure below shows the relationship between the routing table, the FIB, and the adjacency table during central Cisco Express Forwarding mode operation. The Catalyst switches forward traffic from workgroup LANs to a Cisco 7500 series router on the enterprise backbone running central Cisco Express Forwarding. The RP performs the express forwarding.

Distributed CEF Mode Operation

For additional scalability, Cisco Express Forwarding runs in the distributed Cisco Express Forwarding form on certain platforms by spreading processing tasks across two or more line cards. When distributed Cisco Express Forwarding mode is enabled, line cards maintain identical copies of the FIB and adjacency tables. The line cards perform the express forwarding between port adapters, relieving the RP of involvement in the switching operation, thus also enhancing system performance.

Distributed Cisco Express Forwarding uses an interprocess communication (IPC) mechanism to ensure synchronization of FIB tables and adjacency tables on the RP and line cards.

The figure below shows the relationship between the RP and line cards when distributed Cisco Express Forwarding mode is active.

In the Cisco 12000 Series Internet Router, shown in the figure above, the line cards perform the switching. In other routers where you can mix various types of cards in the same router, all cards might not support distributed Cisco Express Forwarding. When a line card that does not support distributed Cisco Express Forwarding receives a packet on one of these other routers, the line card forwards the packet to the next higher switching layer (the RP). This structure allows legacy interface processors to exist in the router with newer interface processors.

Note

The Cisco 12000 Series Internet routers operate only in distributed Cisco Express Forwarding mode.

CEF Features Enabled by Default

- Per-destination load balancing and the universal load sharing algorithm

- Distributed tunnel switching

- Multipoint generic routing encapsulation (GRE) tunnels

- CEF Distributed Tunnel Switching

- CEF-Switched Multipoint GRE Tunnels

CEF Distributed Tunnel Switching

Cisco Express Forwarding supports distributed tunnel switching, such as that made possible by generic routing encapsulation (GRE) tunnels. Distributed tunnel switching is enabled automatically when you enable Cisco Express Forwarding or distributed Cisco Express Forwarding. You do not perform any additional tasks to enable distributed tunnel switching once you enable Cisco Express Forwarding or distributed Cisco Express Forwarding.

CEF-Switched Multipoint GRE Tunnels

The Cisco Express Forwarding-Switched Multipoint GRE Tunnels feature enables Cisco Express Forwarding switching of IP traffic to and from multipoint GRE tunnels. Traffic can be forwarded to a prefix through a tunnel destination when both the prefix and the tunnel destination are specified by the application. GRE creates a virtual point-to-point link to other routers at remote points over an IP internetwork. GRE can encapsulate a wide variety of protocol type packets. By connecting multiprotocol subnetworks in a single-protocol backbone environment, IP tunneling using GRE allows network expansion across a single-protocol backbone environment.

Links for the CEF Features

The table below contains links to information about features that you can configure for use with Cisco Express Forwarding or distributed Cisco Express Forwarding operation.

Features to Configure for Cisco Express Forwarding or Distributed Cisco Express Forwarding Operation

For Information on This Feature...

See the Following Document...

Configuring and verifying basic Cisco Express Forwarding operation

Configuring Basic Cisco Express Forwarding for Improved Performance, Scalability, and Resiliency in Dynamic Networks

Enabling or disabling Cisco Express Forwarding or distributed Cisco Express Forwarding switching and forwarding

Enabling or Disabling Cisco Express Forwarding or Distributed Cisco Express Forwarding to Customize Switching and Forwarding for Dynamic Networks

Changing your load-balancing scheme

Configuring a Load-Balancing Scheme for Cisco Express Forwarding Traffic

Refreshing or rebuilding adjacency or Cisco Express Forwarding tables

Configuring Epochs to Clear and Rebuild Cisco Express Forwarding and Adjacency Tables

Configuring Cisco Express Forwarding consistency checkers

Configuring Cisco Express Forwarding Consistency Checkers for Route Processors and Line Cards

Configuring network accounting for Cisco Express Forwarding

Configuring Cisco Express Forwarding Network Accounting

Customizing the display of recorded Cisco Express Forwarding events

Customizing the Display of Recorded Cisco Express Forwarding Events

How to Configure CEF

There are no tasks for configuring Cisco Express Forwarding. Cisco Express Forwarding is enabled by default on most Cisco devices running Cisco software.

See the “Related Documents” section for links to configuration information for Cisco Express Forwarding features and services.

Configuration Examples for CEF

There are no configuration examples for the Cisco Express Forwarding.

See the “Related Documents” section for links to configuration information for Cisco Express Forwarding features and services.

Where to Go Next

See the "Related Documents" section for links to configuration information for Cisco Express Forwarding features and services.

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

IP switching commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples.

Cisco IOS IP Switching Command Reference

Tasks for verifying Cisco Express Forwarding information on your router

Configuring Basic Cisco Express Forwarding for Improved Performance, Scalability, and Resiliency in Dynamic Networks

Tasks for enabling or disabling Cisco Express Forwarding or distributed Cisco Express Forwarding

Enabling or Disabling Cisco Express Forwarding or Distributed Cisco Express Forwarding to Customize Switching and Forwarding for Dynamic Networks

Tasks for configuring a load-balancing scheme for Cisco Express Forwarding

Configuring a Load-Balancing Scheme for Cisco Express Forwarding Traffic

Tasks for configuring Cisco Express Forwarding consistency checkers

Configuring Cisco Express Forwarding Consistency Checkers for Route Processors and Line Cards

Tasks for configuring epochs for Cisco Express Forwarding tables

Configuring Epochs to Clear and Rebuild Cisco Express Forwarding and Adjacency Tables

Tasks for configuring and verifying Cisco Express Forwarding network accounting

Configuring Cisco Express Forwarding Network Accounting

Tasks for customizing the display of recorded Cisco Express Forwarding events

Customizing the Display of Recorded Cisco Express Forwarding Events

Verification steps for Cisco Express Forwarding switching

Click Here How to Verify Cisco Express Forwarding Switching

Troubleshooting tips for incomplete adjacencies

Click Here Troubleshooting Incomplete Adjacencies with CEF

Description and use of the Cisco Express Forwarding consistency checkers available for the Cisco 7500 and 12000 series routers

Troubleshooting Prefix Inconsistencies with Cisco Express Forwarding

Information about troubleshooting Cisco Express Forwarding routing loops and suboptimal routing

Troubleshooting Cisco Express Forwarding Routing Loops

Causes of common Cisco Express Forwarding-related error messages on platforms running distributed Cisco Express Forwarding switching (Cisco 7500 series routers and Cisco 12000 Series Internet routers) and how to troubleshoot them

Troubleshooting Cisco Express Forwarding-Related Error Messages

Explanation of and troubleshooting information for the Cisco IOS software implementation of Layer 3 load balancing across multiple parallel links when Cisco Express Forwarding is used

Troubleshooting Load Balancing Over Parallel Links Using Cisco Express Forwarding

Troubleshooting guide for unicast IP routing on Catalyst 6500/6000 switches with Supervisor Engine 2, Policy Feature Card 2 (PFC2), or Multilayer Switch Feature Card 2 (MSFC2)

Click Here

QoS features that require Cisco Express Forwarding

When Is CEF Required for Quality of Service

Standards

Standard

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

--

MIBs

MIB

MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

Click Here

RFCs

RFC

Title

RFC 1701

Generic Route Encapsulation (GRE)

RFC 2784

Generic Routing Encapsulation (GRE)

RFC 2890

Key and Sequence Number Extensions to GRE

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

Click Here

Feature Information for CEF

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.

Feature Information for Cisco Express Forwarding Overview

Feature Name

Releases

Feature Configuration Information

Cisco Express Forwarding-Switched Multipoint GRE Tunnels

12.2(8)T

This feature enables Cisco Express Forwarding switching of IP traffic to and from multipoint GRE tunnels. Prior to the introduction of this feature, only process switching was available for multipoint GRE tunnels.

CEF Support for IP Routing between IEEE 802.1Q vLANs

Cisco IOS XE Release 2.1 15.0(1)S

This feature was introduced on Cisco ASR 1000 Series Routers.

This feature was integrated into Cisco IOS Release 15.0(1)S.

Glossary

adjacency --A relationship formed between selected neighboring routers and end nodes for the purpose of exchanging routing information. Adjacency is based upon the use of a common media segment by the routers and nodes involved.

Cisco Express Forwarding --A Layer 3 switching technology. Cisco Express Forwarding can also refer to central Cisco Express Forwarding mode, one of two modes of Cisco Express Forwarding operation. Cisco Express Forwarding enables a Route Processor to perform express forwarding. Distributed Cisco Express Forwarding is the other mode of Cisco Express Forwarding operation.

distributed Cisco Express Forwarding --A mode of Cisco Express Forwarding operation in which line cards (such as Versatile Interface Processor (VIP) line cards) maintain identical copies of the forwarding information base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters; this relieves the Route Switch Processor of involvement in the switching operation.

FIB --forwarding information base. A component of Cisco Express Forwarding that is conceptually similar to a routing table or information base. The router uses the FIB lookup table to make destination-based switching decisions during Cisco Express Forwarding operation. The router maintains a mirror image of the forwarding information in an IP routing table.

GRE --generic routing encapsulation. A tunneling protocol developed by Cisco that enables encapsulation of a wide variety of protocol packet types inside IP tunnels, creating a virtual point-to-point link to Cisco routers at remote points over an IP internetwork. By connecting multiprotocol subnetworks in a single-protocol backbone environment, IP tunneling using GRE allows the expansion of a network across a single-protocol backbone environment.

IPC --interprocess communication. The mechanism that enables the distribution of Cisco Express Forwarding tables from the Route Switch Processor (RSP) to the line card when the router is operating in distributed Cisco Express Forwarding mode.

label disposition --The removal of Multiprotocol Label Switching (MPLS) headers at the edge of a network. In MPLS label disposition, packets arrive on a router as MPLS packets and, with the headers removed, are transmitted as IP packets.

label imposition --The action of putting a label on a packet.

LER --label edge router. A router that performs label imposition.

LFIB --label forwarding information base. The data structure used by switching functions to switch labeled packets.

LIB --label information base. A database used by a label switch router (LSR) to store labels learned from other LSRs, as well as labels assigned by the local LSR.

line card --A general term for an interface processor that can be used in various Cisco products. For example, a Versatile Interface Processor (VIP) is a line card for the Cisco 7500 series router.

LSP --label switched path. A sequence of hops (Router 0...Router n). A packet travels from R0 to Rn by means of label switching mechanisms. An LSP can be chosen dynamically, based on normal routing mechanisms, or it can be configured manually.

LSR --label switch router. A Layer 3 router that forwards a packet based on the value of a label encapsulated in the packet.

MPLS --Multiprotocol Label Switching. An emerging industry standard for the forwarding of packets along the normal routing paths (sometimes called MPLS hop-by-hop forwarding).

prefix --The network address portion of an IP address. A prefix is specified by a network and mask and is generally represented in the format network/mask. The mask indicates which bits are the network bits. For example, 1.0.0.0/16 means that the first 16 bits of the IP address are masked, making them the network bits. The remaining bits are the host bits. In this example, the network number is 10.0.

RIB --Routing Information Base. A central repository of routes that contains Layer 3 reachability information and destination IP addresses or prefixes. The RIB is also known as the routing table.

RP --Route Processor. The processor module in the Cisco 7000 series routers that contains the CPU, system software, and most of the memory components that are used in the router. It is sometimes called a supervisory processor.

RSP --Route Switch Processor. The processor module used in the Cisco 7500 series routers that integrates the functions of the Route Processor (RP) and the Switch Processor (SP).

SP --Switch Processor. The Cisco 7000-series processor module that acts as the administrator for all CxBus activities. It is sometimes called a CiscoBus controller.

VIP --Versatile Interface Processor. An interface card used in Cisco 7000 and Cisco 7500 series routers. The VIP provides multilayer switching and runs Cisco IOS.

VPN --Virtual Private Network. A router configuration that enables IP traffic to use tunneling to travel securely over a public TCP/IP network.

VRF --A Virtual Private Network (VPN) routing/forwarding instance. A VRF consists of an IP routing table, a derived forwarding table, a set of interfaces that use the forwarding table, and a set of rules and routing protocols that determine what goes into the forwarding table. In general, a VRF includes the routing information that defines a customer VPN site that is attached to a PE router.

Chapter 2. Configuring Basic Cisco Express Forwarding

This module contains information about Cisco Express Forwarding and describes the required and optional tasks for verifying Cisco Express Forwarding and distributed Cisco Express Forwarding operation.

Cisco Express Forwarding is an advanced Layer 3 IP switching technology. It optimizes network performance and scalability for all kinds of networks: those that carry small amounts of traffic and those that carry large amounts of traffic in complex patterns, such as the Internet, and networks characterized by intensive web-based applications or interactive sessions.

- Finding Feature Information

- Prerequisites for Cisco Express Forwarding

- Restrictions for Cisco Express Forwarding

- Information About Cisco Express Forwarding

- How to Configure Basic Cisco Express Forwarding

- How to Verify Basic Cisco Express Forwarding

- Configuration Examples for Basic CEF

- Where to Go Next

- Additional References

- Feature Information for Basic CEF

- Glossary

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to Click Here . An account on Cisco.com is not required.

Prerequisites for Cisco Express Forwarding

Cisco Express Forwarding requires a software image that includes Cisco Express Forwarding and IP routing enabled on the device.

Restrictions for Cisco Express Forwarding

Cisco Express Forwarding has the following restrictions:

- The Cisco 12000 Series Internet routers operate only in distributed Cisco Express Forwardingmode.

- If you enable Cisco Express Forwarding and then create an access list that uses the logkeyword, the packets that match the access list are not Cisco Express Forwarding switched. They are process switched. Logging disables Cisco Express Forwarding.

Information About Cisco Express Forwarding

If your network architecture requires that you disable or reenable Cisco Express Forwarding or distributed Cisco Express Forwarding switching and forwarding, change your load balancing scheme, refresh Cisco Express Forwarding tables, configure network accounting for Cisco Express Forwarding, or customize the display of Cisco Express Forwarding events, go to the "Related Documents" section for links to information on these tasks. Otherwise, you need do nothing more to configure Cisco Express Forwarding or distributed Cisco Express Forwarding operation in your network.

Note

Cisco Express Forwarding is supported on interfaces on which IEEE 802.1Q encapsulation has been enabled at the subinterface level. You no longer need to disable CEF operation on interfaces that are using IEEE 802.1Q encapsulation on VLAN subinterfaces.

- Cisco Platform Support for CEF and dCEF

- Cisco Express Forwarding Benefits

- Main Components for CEF Operation

- CEF Operation Modes Central and Distributed

Cisco Platform Support for CEF and dCEF

Cisco Express Forwarding is enabled by default on most Cisco platforms running Cisco IOS software Release 12.0 and later. When Cisco Express Forwarding in enabled on a router, the Route Processor (RP) performs the express forwarding.

To find out if Cisco Express Forwarding is enabled by default on your platform, enter the show ip cefcommand. If Cisco Express Forwarding is enabled, you receive output that looks like the following:

Router# show ip cef
Prefix              Next Hop            Interface
[...]
10.2.61.8/24        192.168.100.1       FastEthernet1/0/0
192.168.101.1       FastEthernet6/1
[...]

If Cisco Express Forwarding is not enabled on your platform, the output for the show ip cefcommand looks like this:

Router# show ip cef
%CEF not running

Distributed Cisco Express Forwarding is enabled by default on the Catalyst 6500 series switch, the Cisco 7500 series router, and the Cisco 12000 Series Internet Router. When distributed Cisco Express Forwarding is enabled on your platform, the line cards perform the express forwarding.

If Cisco Express Forwarding is not enabled on your platform, use the ip cefcommand to enable Cisco Express Forwarding or the ip cef distributed command to enable distributed Cisco Express Forwarding.

Cisco Express Forwarding Benefits

- Improved performance--Cisco Express Forwarding is less CPU-intensive than fast switching route caching. As a result, more CPU processing power can be dedicated to Layer 3 services such as quality of service (QoS) and encryption.

- Scalability--Cisco Express Forwarding offers full switching capacity at each line card when distributed Cisco Express Forwarding mode is active. Distributed Cisco Express Forwarding is a distributed switching mechanism that scales linearly with the number of interface cards and the bandwidth installed in the router.

- Resiliency--Cisco Express Forwarding offers an unprecedented level of switching consistency and stability in large dynamic networks. In dynamic networks, fast-switched cache entries are frequently invalidated by routing changes. These changes can cause traffic to be process-switched through use of the routing table, rather than fast-switched through use of the route cache. Because the forwarding information base (FIB) lookup table contains all known routes that exist in the routing table, it eliminates the need for route cache maintenance and the steps involved with fast-switch or process-switch forwarding. Cisco Express Forwarding can switch traffic more efficiently than typical demand caching schemes.

Main Components for CEF Operation

Information conventionally stored in a route cache is stored in several data structures for Cisco Express Forwarding switching. The data structures provide optimized lookup for efficient packet forwarding. The two main components of Cisco Express Forwarding operation are the forwarding information base (FIB) and the adjacency tables.

The FIB is conceptually similar to a routing table or information base. A router uses this lookup table to make destination-based switching decisions during Cisco Express Forwarding operation. The FIB is updated as changes occur in the network and contains all routes known at the time. For more information on the FIB, see the "Cisco Express Forwarding Overview" module.

Adjacency tables maintain Layer 2 next-hop addresses for all FIB entries. For more information on adjacency tables, see the "Cisco Express Forwarding Overview" module.

This separation of the reachability information (in the Cisco Express Forwarding table) and the forwarding information (in the adjacency table), provides two main benefits:

- The adjacency table can be built separately from the Cisco Express Forwarding table, allowing both tables to build without the process switching of any packets.

- The MAC header rewrite used to forward a packet isn't stored in cache entries, so changes in a MAC header rewrite string do not require invalidation of cache entries.

CEF Operation Modes Central and Distributed

- Central Cisco Express Forwarding Mode Operation

- Distributed Cisco Express Forwarding Mode Operation

Central Cisco Express Forwarding Mode Operation

You can use central Cisco Express Forwarding mode when line cards are not available for Cisco Express Forwarding switching, when you need to use features not compatible with distributed Cisco Express Forwarding switching, or when you are running on a platform that is not a distributed platform. When central Cisco Express Forwarding mode is enabled, the Cisco Express Forwarding FIB and adjacency tables reside on the RP, and the RP performs the express forwarding.

The figure below shows the relationship between the routing table, the FIB, and the adjacency table during central Cisco Express Forwarding mode operation. The Catalyst switches forward traffic from workgroup LANs to a Cisco 7500 series router on the enterprise backbone running central Cisco Express Forwarding. The RP performs the express forwarding.

Distributed Cisco Express Forwarding Mode Operation

For additional scalability, Cisco Express Forwarding runs in the form of distributed Cisco Express Forwarding on certain platforms by spreading processing tasks across two or more line cards. When distributed Cisco Express Forwarding mode is enabled, line cards maintain identical copies of the FIB and adjacency tables. The line cards perform the express forwarding between port adapters, relieving the RP of involvement in the switching operation, thus also enhancing system performance.

Distributed Cisco Express Forwarding uses an interprocess communication (IPC) mechanism to ensure synchronization of FIB tables and adjacency tables on the RP and line cards.

The figure below shows the relationship between the RP and line cards when distributed Cisco Express Forwarding mode is active.

In the Cisco 12000 Series Internet Router, shown in the figure above, the line cards perform the switching. In other routers, where you can mix various types of cards in the same router, all cards might not support distributed Cisco Express Forwarding. When a line card that does not support distributed Cisco Express Forwarding receives a packet on one of these other routers, the line card forwards the packet to the next higher switching layer (the RP). This structure allows legacy interface processors to exist in the router with newer interface processors.

Note

The Cisco 12000 Series Internet routers operate only in distributed Cisco Express Forwarding mode.

How to Configure Basic Cisco Express Forwarding

There are no configuration tasks. Cisco Express Forwarding is enabled by default.

How to Verify Basic Cisco Express Forwarding

The following section contains instructions for verifying basic Cisco Express Forwarding or distributed Cisco Express Forwarding operation.

Before you perform the remaining tasks in this section you need to know which mode of Cisco Express Forwarding is running on your router. Cisco Express Forwarding is enabled by default on the Cisco 7100, 7200, and 7500 series routers. Distributed Cisco Express Forwarding is enabled by default on the Catalyst 6500 switch and on Cisco 12000 Series Internet routers. To determine if Cisco Express Forwarding or distributed Cisco Express Forwarding is enabled on your router, you can enter the show ip interface command and look for the entry "IP CEF switching enabled" or "IP Distributed CEF switching enabled." If Cisco Express Forwarding is not enabled, the entry in the command display would indicate that "IP CEF switching is disabled."

To verify basic Cisco Express Forwarding or distributed Cisco Express Forwarding operation, perform the following procedures and tasks:

- Determining How the Router Is Configured

- Verifying Cisco Express Forwarding Operation

- Verifying Distributed Cisco Express Forwarding Operation

- Interpreting Cisco Express Forwarding Command Output

Determining How the Router Is Configured

To determine if the router is configured for Cisco Express Forwarding or distributed Cisco Express Forwarding, perform the following task.

SUMMARY STEPS

1.    enable

2.    show ip interface [type number] [brief]

3.    exit

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

show ip interface [type number] [brief]

Example:

Router# show ip interface

Displays the usability status of interfaces configured for IP.

- The type argument is the interface type.

- The number argument is the interface number.

- The brief keyword displays a summary of the usability status information.

Look for the entry "IP CEF switching enabled" or "IP Distributed CEF switching enabled."

Step 3

exit

Example:

Router# exit

Exits to user EXEC mode.

- What to Do Next

What to Do Next

Verifying Cisco Express Forwarding Operation

Perform the following tasks, in the order presented, to verify Cisco Express Forwarding operation on your router or to look for Cisco Express Forwarding operation information on your router:

See the Verifying Distributed Cisco Express Forwarding Operation for the tasks to perform for d istributed Cisco Express Forwarding operation.

- Verifying That Cisco Express Forwarding Switching Is Enabled

- Locating the Prefix in a Forwarding Table on the RP

- Finding the Cisco Express Forwarding Output Information

- Verifying the Adjacency or Next-Hop Information

Verifying That Cisco Express Forwarding Switching Is Enabled

To verify tha Cisco Express Forwarding switching is enabled on the input (ingress) interface on the router, perform the following steps.

SUMMARY STEPS

1.    enable

2.    show ip cef

3.    show cef interface type number detail

4.    show ip interface type number

5.    exit

DETAILED STEPS

Step 1

enable

Use this command to enable privileged EXEC mode. You can also enter this command in user EXEC mode. Enter your password if prompted. For example:

Example:

Router> enable
Router#

Step 2

show ip cef

Use this command to verify that Cisco Express Forwarding is enabled globally. For example:

Example:

Router# show ip cef
%CEF not running

If Cisco Express Forwarding is not running, use the ip cefcommand to enable Cisco Express Forwarding or the ip cef distributed command to enable distributed Cisco Express Forwarding.

When Cisco Express Forwarding or distributed Cisco Express Forwarding is enabled, the show ip cefcommand shows a brief display of all FIB entries.

Step 3

show cef interface type number detail

Use this command to verify that Cisco Express Forwarding is enabled on a particular ingress interface. Look for the entry "IP CEF switching enabled." For example:

Example:

Router# show cef interface fastethernet 1/0/0 detail
FastEthernet1/0/0 is up (if_number 9)
Corresponding hwidb fast_if_number 9
Corresponding hwidb firstsw->if_number 9
Internet address is 10.2.61.8/24
ICMP redirects are always sent
Per packet load-sharing is disabled
IP unicast RPF check is disabled
Inbound access list is not set
Outbound access list is not set
IP policy routing is disabled
Hardware idb is FastEthernet1/0/0
Fast switching type 1, interface type 5
IP CEF switching enabled
IP Feature Fast switching turbo vector
IP Feature CEF switching turbo vector
Input fast flags 0x0, Output fast flags 0x0
ifindex 7(7)
Slot 1 Slot unit 0 VC -1
Transmit limit accumulator 0x48001A82 (0x48001A82)
IP MTU 1500

Step 4

show ip interface type number

Use this command to display the Cisco IOS switching methods enabled on an interface. For example:

Example:

router# show ip interface fastethernet 1/0/0

FastEthernet1/0/0 is up, line protocol is up

IP fast switching is enabled
IP fast switching on the same interface is enabled
IP Flow switching is disabled
IP CEF switching is enabled
IP Distributed switching is enabled
IP Fast switching turbo vector
IP Normal CEF switching turbo vector
IP multicast fast switching is enabled
IP multicast distributed fast switching is disabled
IP route-cache flags are Fast, Distributed, No CEF

In the above output, the "IP CEF switching is enabled" entry indicates that Cisco Express Forwarding is enabled by default. The "No CEF" IP route-cache flag indicates that Cisco Express Forwarding is disabled because an administrator entered the no ip route-cache cefcommand on this interface.

To enable Cisco Express Forwarding on this interface, enter the ip route-cache cef command. Once you do that, the "CEF" flag indicates that Cisco Express Forwarding is running.

Step 5

exit

Use this command to exit privileged EXEC mode. For example:

Example:

Router# exit
Router>

Locating the Prefix in a Forwarding Table on the RP

To locate the prefix in a forwarding table, perform the following steps.

SUMMARY STEPS

1.    enable

2.    show ip cef

3.    show ip cef vrf vrf-name

4.    Repeat Step 2 as many times as required to locate the prefix.

5.    exit

DETAILED STEPS

Step 1

enable

Use this command to enable privileged EXEC mode. You can also enter this command in user EXEC mode. Enter your password if prompted. For example:

Example:

Router> enable
Router#

Step 2

show ip cef

Use this command to show entries in the FIB and confirm that prefixes are listed in the FIB. For example:

Example:

Router# show ip cef
Prefix              Next Hop            Interface
[...]
10.2.61.8/24        192.168.100.1       FastEthernet1/0/0
192.168.101.1       FastEthernet6/1
[...]

Step 3

show ip cef vrf vrf-name

Use this command to locate prefixes in forwarding tables associated with Virtual Private Network (VPN) routing/forwarding table instances (VRFs). For example, this command shows prefixes in the left-hand column for a VRF named vpn1:

Example:

Router# show ip cef vrf vpn1
Prefix              Next Hop            Interface
0.0.0.0/32          receive
10.1.0.0/8          10.0.0.1            Ethernet1/3
10.2.0.0/8          10.0.0.2            POS6/0
10.0.0.0/8          attached            Ethernet1/3
10.0.0.0/32         receive
10.0.0.1/32         10.0.0.1            Ethernet1/3
10.0.0.2/32         receive
10.255.255.255/32   receive
10.3.0.0/8          10.0.0.2            POS6/0
10.50.0.0/24        receive
255.255.255.255/32  receive

Step 4

Repeat Step 2 as many times as required to locate the prefix.
If Cisco Express Forwarding is in a VPN, you might need to look at multiple VRFs.

Step 5

exit

Use this command to exit privileged EXEC mode. For example:

Example:

Router# exit
Router>

Finding the Cisco Express Forwarding Output Information

To find the Cisco Express Forwarding output information associated with the prefix on the RP, perform the following steps.

SUMMARY STEPS

1.    enable

2.    show ip cef

3.    show ip cef prefix

4.    show ip cef prefix detail

5.    exit

DETAILED STEPS

Step 1

enable

Use this command to enable privileged EXEC mode. You can also enter this command in user EXEC mode. Enter your password if prompted. For example:

Example:

Router> enable
Router#

Step 2

show ip cef

Use this command to confirm that the prefix is listed in the FIB. For example:

Example:

router# show ip cef
Prefix              Next Hop            Interface
0.0.0.0/32          receive
192.168.0.0/30      attached            Serial2/0/0:1
192.168.0.0/32      receive
10.2.61.8/24        192.168.100.1       FastEthernet1/0/0

Step 3

show ip cef prefix

Use this command to display the prefix entry in the FIB for centralized Cisco Express Forwarding. For example:

Example:

Router# show ip cef 10.2.61.8 255.255.255.0
10.0.0.0/8, version 72, per-destination sharing
0 packets, 0 bytes
via 192.168.100.1, 0 dependencies, recursive
traffic share 1
next hop 192.168.100.1, FastEthernet1/0/0 via 192.168.100.1/32
valid adjacency
via 192.168.101.1, 0 dependencies, recursive
traffic share 1
next hop 192.168.101.1, FastEthernet6/1 via 192.168.101.1/32
valid adjacency
0 packets, 0 bytes switched through the prefix

Step 4

show ip cef prefix detail

Use this command to show more detail for each of the active paths associated with a destination prefix. For example:

Example:

Router# show ip cef 10.0.0.0 detail
10.0.0.0/8, version 72, per-destination sharing
0 packets, 0 bytes
via 192.168.100.1, 0 dependencies, recursive
traffic share 1
next hop 192.168.100.1, FastEthernet1/0/0 via 192.168.100.1/32
valid adjacency
via 192.168.101.1, 0 dependencies, recursive
traffic share 1
next hop 192.168.101.1, FastEthernet6/1 via 192.168.101.1/32
valid adjacency
0 packets, 0 bytes switched through the prefix

Step 5

exit

Use this command to exit privileged EXEC mode. For example:

Example:

Router# exit
Router>

Verifying the Adjacency or Next-Hop Information

To verify the adjacency or next-hop information on the RP, perform the following steps.

Adjacencies are added to the adjacency table when the adjacency is

- Indirectly configured manually

- Dynamically discovered through ARP

- Created when a routing protocol, for example, Border Gateway Protocol (BGP) or Open Shortest Path First (OSPF), forms a neighbor relationship

For more information on adjacencies, see the "Cisco Express Forwarding Overview" module.

SUMMARY STEPS

1.    enable

2.    show ip cef

3.    show adjacency detail

4.    show adjacency summary

5.    show adjacency type number

6.    show ip cef exact-route source-address destination-address

7.    exit

DETAILED STEPS

Step 1

enable

Use this command to enable privileged EXEC mode. You can also enter this command in user EXEC mode. Enter your password if prompted. For example:

Example:

Router> enable
Router#

Step 2

show ip cef

Use this command to find the output interface. For example:

Example:

router# show ip cef
Prefix              Next Hop            Interface
0.0.0.0/32          receive
192.168.0.0/30      attached            Serial2/0/0:1
192.168.0.0/32      receive
10.2.61.8/24        192.168.100.1       FastEthernet1/0/0

In this example, the output interface for the prefix 10.2.61.8/24 is FastEthernet 1/0/0, and the next hop address is 192.168.100.1.

Step 3

show adjacency detail

Use this command to display adjacency information, including Layer 2 information. For example:

Example:

Router# show adjacency detail
Protocol Interface                 Address
IP       Ethernet1/0/0             10.2.61.8(7)
0 packets, 0 bytes
00107BC30D5C
00500B32D8200800
ARP        02:01:49

The encapsulation string 00107BC30D5C00500B32D8200800 is that of an adjacency used for traffic switched out of a router on an Ethernet link by means of Ethernet II encapsulation.

Step 4

show adjacency summary

Use this command to display Cisco Express Forwarding adjacency table summary information. For example:

Example:

Router# show adjacency summary
Adjacency Table has 1 adjacency
Interface                 Adjacency Count
Ethernet1/0/0             1

Step 5

show adjacency type number

Use this command to display adjacency information for a particular interface. For example:

Example:

Router# show adjacency fastethernet 2/3
Protocol  Interface                  Address
IP        FastEthernet2/3            172.20.52.1(3045)
IP        FastEthernet2/3            172.20.52.22(11)

Step 6

show ip cef exact-route source-address destination-address

Use this command to display the exact route for a source-destination IP address pair and verify the next-hop address. For example:

Example:

Router# show ip cef exact-route 10.1.1.1 10.2.61.8
10.1.1.1         -> 10.2.61.8 :FastEthernet1/0/0 (next hop 192.168.100.1)

In this example, the exact route from source address 10.1.1.1 to destination address 10.2.61.8 is through interface Ethernet1/0/0 to next hop address 192.168.100.1.

Step 7

exit

Use this command to exit privileged EXEC mode. For example:

Example:

Router# exit
Router>

Verifying Distributed Cisco Express Forwarding Operation

Perform the following tasks, in the order presented, to verify distributed Cisco Express Forwarding operation on your router:

- Cisco Express Forwarding Command Syntax on Line Cards

- Verifying That dCEF Switching Is Enabled

- Locating the Prefix in a Forwarding Table on a Line Card

- Finding the Distributed Cisco Express Forwarding Output Information

- Verifying the Adjacency or Next-Hop Information on a Line Card

Cisco Express Forwarding Command Syntax on Line Cards

To perform tasks on router line cards, you need to use the following syntax: execute-on[slot slot-number | all] command. The execute-on commands apply only to the Cisco 12000 Series Internet routers and the Cisco 7500 series routers. The all keyword is available only on the Cisco 12000 Series Internet routers.

For example, use the following command to display FIB entries on the line cards in the first slot:

Router# execute-on 0
show ip cef

To perform tasks on a Catalyst 6500 series switch, you use the following syntax: remote command module mod command. For example:

Router# remote command module 2 show ip cef

The tasks in this document apply to the Cisco 7500 series and Cisco 12000 Series Internet routers.

Verifying That dCEF Switching Is Enabled

To verify that distributed Cisco Express Forwarding switching is enabled on the input (ingress) interface on the line card, perform the following steps.

SUMMARY STEPS

1.    enable

2.    show ip cef

3.    execute-on slot slot-number show ip cef prefix

4.    exit

DETAILED STEPS

Step 1

enable

Use this command to enable privileged EXEC mode. You can also enter this command in user EXEC mode. Enter your password if prompted. For example:

Example:

Router> enable
Router#

Step 2

show ip cef

Use this command to verify that Cisco Express Forwarding is enabled globally. For example:

Example:

Router# show ip cef
%CEF not running

If Cisco Express Forwarding is not running, use the ip cefcommand to enable (central) Cisco Express Forwarding or the ip cef distributed command to enable distributed Cisco Express Forwarding.

When Cisco Express Forwarding or distributed Cisco Express Forwarding is enabled, the show ip cefcommand shows a brief display of all FIB entries.

Step 3

execute-on slot slot-number show ip cef prefix

Use this command to verify information about interfaces on a line card. For example:

Example:

Router# execute-on slot 0
show ip cef 192.68.0.0 255.255.255.0
show ip cef 192.68.0.0 255.255.255.0 from slot 0:
192.68.0.0/24, version 19, epoch 0, attached, connected
0 packets, 0 bytes
via Ethernet5/0/0, 0 dependencies
valid glean adjacency

Step 4

exit

Use this command to exit privileged EXEC mode. For example:

Example:

Router# exit
Router>

Locating the Prefix in a Forwarding Table on a Line Card

To locate the prefix in a forwarding table on the line card, perform the following steps.

SUMMARY STEPS

1.    enable

2.    execute-on slot slot-number show ip cef

3.    execute-on all show ip cef vrf vrf-name

4.    Repeat Step 2 as many times as required to locate the prefix.

5.    show ip cef

6.    exit

DETAILED STEPS

Step 1

enable

Use this command to enable privileged EXEC mode. You can also enter this command in user EXEC mode. Enter your password if prompted. For example:

Example:

Router> enable
Router#

Step 2

execute-on slot slot-number show ip cef

Use this command to show entries in the FIB on the line card and confirm that prefixes are listed in the FIB. For example:

Example:

Router# execute-on slot 0 show ip cef
show ip cef from slot 0:
Prefix              Next Hop             Interface
0.0.0.0/0            192.168.0.1          Ethernet5/0/0
0.0.0.0/32           receive
192.168.0.0/24       attached             Ethernet5/0/0
192.168.0.0/32       receive
192.168.0.1/32       192.168.0.1          Ethernet5/0/0
192.168.0.141/32     receive
192.168.0.255/32     receive
239.224.0.0/4        drop
239.224.0.0/24       receive
255.255.255.255/32   receive

Step 3

execute-on all show ip cef vrf vrf-name

Use this command to locate prefixes in forwarding tables associated with Virtual Private Network (VPN) routing/forwarding instances (VRFs). For example, this command shows prefixes in the left-hand column for a VRF named vpn1:

Example:

Router# execute-on all show ip cef vrf vpn1
Prefix              Next Hop            Interface
0.0.0.0/32          receive
10.1.0.0/8          10.0.0.1            Ethernet1/3
10.2.0.0/8          10.0.0.2            POS6/0
10.0.0.0/8          attached            Ethernet1/3
10.0.0.0/32         receive
10.0.0.1/32         10.0.0.1            Ethernet1/3
10.0.0.2/32         receive
10.255.255.255/32   receive
10.3.0.0/8          10.0.0.2            POS6/0
10.50.0.0/24        receive
255.255.255.255/32  receive

Step 4

Repeat Step 2 as many times as required to locate the prefix.
If distributed Cisco Express Forwarding is in a VPN, you might need to look at multiple VRFs.

Step 5

show ip cef

Use this command to show entries in the FIB on the RP and to verify that the FIB on the line card is synchronized with the FIB maintained by the router. For example:

Example:

Router# show ip cef
Prefix              Next Hop            Interface
[...]
10.2.61.8/24        192.168.100.1       FastEthernet1/0/0
192.168.101.1       FastEthernet6/1
[...]

Compare the prefixes, next hops, and interfaces in this output with those in the output from Step 1 to verify that FIB on the line card is synchronized with the FIB maintained by the router.

Step 6

exit

Use this command to exit privileged EXEC mode. For example:

Example:

Router# exit
Router>

Finding the Distributed Cisco Express Forwarding Output Information

To find the distributed Cisco Express Forwarding output information associated with the prefix on a line card, perform the following steps.

SUMMARY STEPS

1.    enable

2.    execute-on slot slot-number show ip cef

3.    execute-on slot slot-number show ip cef prefix

4.    execute-on slot slot-number show ip cef prefix detail

5.    exit

DETAILED STEPS

Step 1

enable

Use this command to enable privileged EXEC mode. You can also enter this command in user EXEC mode. Enter your password if prompted. For example:

Example:

Router> enable
Router#

Step 2

execute-on slot slot-number show ip cef

Use this command to confirm that the prefix is listed in the FIB. For example:

Example:

Router# execute-on slot 0
show ip cef
show ip cef from slot 0:
Prefix              Next Hop             Interface
0.0.0.0/0           192.168.0.1           Ethernet5/0/0
0.0.0.0/32          receive
192.168.0.0/24      attached              Ethernet5/0/0
192.168.0.0/32      receive
192.168.0.1/32      192.168.0.1           Ethernet5/0/0
192.168.0.141/32    receive
192.168.0.255/32    receive
239.224.0.0/4       drop
239.224.0.0/24      receive
255.255.255.255/32  receive

Step 3

execute-on slot slot-number show ip cef prefix

Use this command to display the prefix entry in the FIB on a line card. For example:

Example:

Router# execute
-on slot 3 show ip cef 192.68.0.0 255.255.255.0
show ip cef 192.168.0.0 255.255.255.0 from slot 0:
192.168.0.0/24, version 19, epoch 0, attached, connected
0 packets, 0 bytes
via Ethernet5/0/0, 0 dependencies
valid glean adjacency

Step 4

execute-on slot slot-number show ip cef prefix detail

Use this command to show more detail for each of the active paths associated with a destination prefix on a line card. For example:

Example:

Router# execute-on slot 0 show ip cef 10.24.48.32 detail
show ip cef 192.168.0.0 255.255.255.0 from slot 0:
192.168.0.0/24, version 19, epoch 0, attached, connected
0 packets, 0 bytes
via Ethernet5/0/0, 0 dependencies
valid glean adjacency

Step 5

exit

Use this command to exit privileged EXEC mode. For example:

Example:

Router# exit
Router>

Verifying the Adjacency or Next-Hop Information on a Line Card

To verify the adjacency or next-hop information on a line card, perform the following steps.

Cisco Express Forwarding adds an adjacency to the adjacency table when the adjacency is

- Indirectly configured manually

- Dynamically discovered through ARP

- Created when a routing protocol, for example, BGP or OSPF, forms a neighbor relationship

For more information on adjacencies, see the Cisco Express Forwarding Overview module.

SUMMARY STEPS

1.    enable

2.    show ip cef

3.    show adjacency detail

4.    show adjacency summary

5.    show adjacency type number

6.    show ip cef exact-route source-address destination-address

7.    execute-on all show ip cef destination

8.    exit

DETAILED STEPS

Step 1

enable

Use this command to enable privileged EXEC mode. You can also enter this command in user EXEC mode. Enter your password if prompted. For example:

Example:

Router> enable
Router#

Step 2

show ip cef

Use this command to determine the output interface. For example:

Example:

router# show ip cef
Prefix              Next Hop            Interface
0.0.0.0/32          receive
192.168.0.0/30      attached            Serial2/0/0:1
192.168.0.0/32      receive
10.2.61.8/24        192.168.100.1       FastEthernet1/0/0

In this example, the output interface for the prefix 10.2.61.8/24 is FastEthernet 1/0/0, and the next hop address is 192.168.100.1.

Step 3

show adjacency detail

Use this command to display adjacency information, including Layer 2 information. For example:

Example:

Router# show adjacency detail
Protocol Interface                 Address
IP       Ethernet1/0/0             10.2.61.8(7)
0 packets, 0 bytes
00107BC30D5C
00500B32D8200800
ARP        02:01:49

The encapsulation string 00107BC30D5C00500B32D8200800 is that of an adjacency used for traffic switched out of a router on an Ethernet link by means of Ethernet II encapsulation. (The first 12 characters are the MAC address of the destination next-hop interface. The next 12 characters represent the MAC address of the source interface of the packet. The last 4 characters [0x0800] represent the Ethernet II encapsulation value for IP.)

Step 4

show adjacency summary

Use this command to display Cisco Express Forwarding adjacency table summary information. For example:

Example:

Router# show adjacency summary
Adjacency Table has 1 adjacency
Interface                 Adjacency Count
Ethernet1/0/0             1

Step 5

show adjacency type number

Use this command to display adjacency information for a particular interface. For example:

Example:

Router# show adjacency fastethernet 2/3
Protocol  Interface                  Address
IP        FastEthernet2/3            172.20.52.1(3045)
IP        FastEthernet2/3            172.20.52.22(11)

Step 6

show ip cef exact-route source-address destination-address

Use this command to display the exact route for a source-destination IP address pair and verify the next-hop address. For example:

Example:

Router# show ip cef exact-route 10.1.1.1 10.2.61.8
10.1.1.1         -> 10.2.61.8 :FastEthernet1/0/0 (next hop 192.168.100.1)

In this example, the exact route from source address 10.1.1.1 to destination address 10.2.61.8 is through interface Ethernet1/0/0 to next hop address 192.168.100.1.

Step 7

execute-on all show ip cef destination

Use this command to display output interfaces and next hops for all line cards. For example:

Example:

Router# execute-on all show ip cef 10.20.84.32
========= Line Card (Slot 1) =======
10.16.0.0/13, version 408935, cached adjacency 0.0.0.0
0 packets, 0 bytes
Flow: AS 6172, mask 13
via 172.16.213.1, 0 dependencies, recursive
next hop 172.16.213.1, POS1/0.500 via 172.16.213.0/30
valid cached adjacency
========= Line Card (Slot 2) =======
10.16.0.0/13, version 13719, cached adjacency 0.0.0.0
0 packets, 0 bytes
Flow: AS 6172, mask 13
via 172.16.213.1, 0 dependencies, recursive
next hop 172.16.213.1, POS1/0.500 via 172.16.213.0/30
valid cached adjacency

Step 8

exit

Use this command to exit privileged EXEC mode. For example:

Example:

Router# exit
Router>

Interpreting Cisco Express Forwarding Command Output

Perform the following tasks to interpret information in Cisco Express Forwarding command output:

- Verifying That CEF Information Looks As Expected

- Interpreting MPLS Information in CEF Output

Verifying That CEF Information Looks As Expected

Perform the following tasks to verify that the Cisco Express Forwarding information looks as you expected.

SUMMARY STEPS

1.    enable

2.    show ip route

3.    show ip cef

4.    Compare the command output in Steps 2 and 3.

5.    (For distributed Cisco Express Forwarding operation only) execute-on slot slot-number show ip cef

6.    (For distributed Cisco Express Forwarding operation only) Compare the command output in Steps 3 and 5.

7.    exit

DETAILED STEPS

Step 1

enable

Use this command to enable privileged EXEC mode. You can also enter this command in user EXEC mode. Enter your password if prompted. For example:

Example:

Router> enable
Router#

Step 2

show ip route

Use this command to look at the forwarding information contained in the IP routing table. For example:

Example:

Router# show ip route
...
10.1.0.0/32 is subnetted, 1 subnets
O       10.1.2.3 [110/3] via 10.5.5.5, 00:00:03, POS2/0/0
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C       10.5.5.5/32 is directly connected, POS2/0/0
C       10.5.5.0/24 is directly connected, POS2/0/0
10.7.0.0/24 is subnetted, 1 subnets
O       10.7.8.0 [110/3] via 10.5.5.5, 00:00:04, POS2/0/0
10.0.0.0/24 is subnetted, 2 subnets
O       10.23.64.0 [110/12] via 10.5.5.5, 00:00:04, POS2/0/0
O       10.23.66.0 [110/12] via 10.5.5.5, 00:00:04, POS2/0/0
10.47.0.0/32 is subnetted, 1 subnets
O       10.47.0.10 [110/3] via 10.5.5.5, 00:00:04, POS2/0/0
O    172.16.57.0/24 [110/3] via 10.5.5.5, 00:00:04, POS2/0/0
10.150.0.0/24 is subnetted, 1 subnets
C       10.150.3.0 is directly connected, Fddi0/0/0
O    192.168.92.0/24 [110/2] via 10.5.5.5, 00:00:04, POS2/0/0

In the example, c indicates a directly connected route and o represents a route discovered by means of OSPF.

Step 3

show ip cef

Use this command to display entries in the FIB. For example:

Example:

Router# show ip cef
Prefix              Next Hop            Interface
0.0.0.0/0           10.5.5.5             POS2/0/0    (default route)
0.0.0.0/32          receive
10.1.2.3/32         10.5.5.5             POS2/0/0    (two paths)
10.150.3.9           Fddi0/0/0
10.5.5.0/24         attached             POS2/0/0
10.5.5.0/32         receive
10.5.5.5/32         attached             POS2/0/0    (glean adjacency)
10.5.5.6/32         receive                (our interface)
10.5.5.255/32       receive                (broadcast)
10.7.8.0/24         10.5.5.5             POS2/0/0
10.150.3.9           Fddi0/0/0
10.23.64.0/24       10.150.3.9           Fddi0/0/0
10.23.66.0/24       10.150.3.9           Fddi0/0/0    (normal route)
10.47.0.10/32       10.150.3.9           Fddi0/0/0
10.150.3.0/24       attached             Fddi0/0/0
10.150.3.0/32       receive
10.150.3.1/32       receive
10.150.3.255/32     receive
192.168.92.0/24     10.5.5.5             POS2/0/0
10.150.3.9           Fddi0/0/0
172.16.57.0/24      10.5.5.5             POS2/0/0
10.150.3.9           Fddi0/0/0
239.224.0.0/4       receive                (multicast)
255.255.255.255/32  receive                (all 1s broadcast)

Step 4

Compare the command output in Steps 2 and 3.
Cisco Express Forwarding maintains the information contained in the IP routing table structured in a way that optimizes forwarding. Check that there is a one-to-one correlation between FIB entries and routing table entries. For example, the following lines from the sample output in Step 2 and Step 3 show a one-to-one correlation. The destination prefix 192.92.92.0/24, the next hop IP address 10.5.5.5, and the next-hop interface POS2/0/0 are the same.

- From the show ip route command output in Step 2:

Example:

192.168.92.0/24 [110/2] via 10.5.5.5, 00:00:04, POS2/0/0

- From the show ip cef command output in Step 3:

Example:

192.168.92.0/24      10.5.5.5             POS2/0/0

If there is not a one-to-one correlation, you can recreate the central FIB table by clearing the IP routing table and allowing the routing table to be rebuilt, which in turn causes the central FIB table to be repopulated with up-to-date routing information.

Step 5

(For distributed Cisco Express Forwarding operation only) execute-on slot slot-number show ip cef
Use this command to display FIB entries on all line cards. For example:

Example:

Router# execute-on slot 2 show ip cef
show ip cef from slot 2:
Prefix              Next Hop            Interface
0.0.0.0/0           10.5.5.5             POS2/0/0
0.0.0.0/32          receive
10.1.2.3/32         10.5.5.5             POS2/0/0
10.150.3.9           Fddi0/0/0
105.5.5.0/24        attached             POS2/0/0
10.5.5.0/32         receive
10.5.5.5/32         attached             POS2/0/0
10.5.5.6/32         receive
10.5.5.255/32       receive
10.7.8.0/24         10.5.5.5             POS2/0/0
10.150.3.9           Fddi0/0/0
10.7.54.0/24        attached             Fddi0/1/0
10,7.54.0/32        receive
10.7.54.3/32        receive
10.7.54.255/32      receive
10.23.64.0/24       10.150.3.9           Fddi0/0/0
10.23.66.0/24       10.150.3.9           Fddi0/0/0
10.47.0.10/32       10.150.3.9           Fddi0/0/0
10.150.3.0/24       attached             Fddi0/0/0
10.150.3.0/32       receive
10.150.3.1/32       receive
10.150.3.255/32     receive
192.168.92.0/24     10.5.5.5             POS2/0/0
10.150.3.9           Fddi0/0/0
172.16.57.0/24      10.5.5.5             POS2/0/0
10.150.3.9           Fddi0/0/0
239.224.0.0/4       receive
255.255.255.255/32  receive

Step 6

(For distributed Cisco Express Forwarding operation only) Compare the command output in Steps 3 and 5.
The output from the show ip cefcommand in Step 3 should be identical to the output from the execute-on slot 2 show ip cefcommand in Step 5. If the outputs are not identical, see the Configuring Cisco Express Forwarding Consistency Checkers for Route Processors and Line Cards module for information on synchronizing FIB entries on the RP and the line card.

Step 7

exit

Use this command to exit privileged EXEC mode. For example:

Example:

Router# exit
Router>

Interpreting MPLS Information in CEF Output

Perform the following steps to interpret Multiprotocol Label Switching (MPLS) information in Cisco Express Forwarding output.

Cisco Express Forwarding interacts with a label switched path (LSP) primarily at the beginning and end of the LSP--that is, on label imposition (IP packet to MPLS packet) and label disposition (MPLS packet to IP packet). Output from Cisco Express Forwarding commands should show these processes.

The Cisco implementation of MPLS leverages the advantages of Cisco Express Forwarding. When you use a router as an MPLS edge router, Cisco Express Forwarding identifies the route for incoming packets and finds the label to apply to the packet.

However, when you use a router as a label switch router (LSR), tables from the MPLS label forwarding information base (LFIB) are used to switch MPLS packets. These tables are distributed to the Versatile Interface Processor (VIP) or to line cards in the same way that the FIB tables are distributed in Cisco Express Forwarding.

A customer-site VRF contains all the routes available to the site from the VPNs to which it belongs. VPN routing information is stored in the IP routing table and in the Cisco Express Forwarding table for each VRF. A separate set of tables is maintained for each VRF, which prevents information from being forwarded outside a VPN and prevents packets that are outside a VPN from being forwarded to a router within the VPN. Based on the routing information stored in the VRF IP routing table and the VRF Cisco Express Forwarding table, packets are forwarded to their destinations. Output from Cisco Express Forwarding commands shows details from the VRF Cisco Express Forwarding tables.

SUMMARY STEPS

1.    enable

2.    show ip cef vrf vrf-name detail

3.    exit

DETAILED STEPS

Step 1

enable

Use this command to enable privileged EXEC mode. You can also enter this command in user EXEC mode. Enter your password if prompted. For example:

Example:

Router> enable
Router#

Step 2

show ip cef vrf vrf-name detail

Use this command to display detailed information from the Cisco Express Forwarding forwarding table that is associated with a VRF. For example:

Example:

Router# show ip cef vrf vpn1 detail

IP CEF with switching (Table Version 10), flags=0x0
8 routes, 0 reresolve, 0 unresolved (0 old, 0 new)
46 leaves, 51 nodes, 54640 bytes, 361 inserts, 315 invalidations
0 load sharing elements, 0 bytes, 0 references
universal per-destination load sharing algorithm, id F968AD29
5 CEF resets, 38 revisions of existing leaves
refcounts:  1400 leaf, 1392 node
Adjacency Table has 2 adjacencies
0.0.0.0/32, version 0, receive
192.168.6.0/24, version 9, cached adjacency to Serial0/1.1
0 packets, 0 bytes

The following section of the Cisco Express Forwarding output provides MPLS information for the first adjacency. The "tag rewrite" is an equivalent of a Cisco Express Forwarding adjacency. Look at the tags imposed field. The first tag {20} is the tag used to reach the next hop, 10.1.1.13. The second tag {30} is the tag advertised to the local provider edge (PE) router by the remote PE router.

Example:

tag information set
local tag: VPN-route-head
fast tag rewrite with Se0/1.1, point2point, tags imposed: {20 30}
via 10.10.10.6, 0 dependencies, recursive
next hop 10.1.1.13, Serial0/1.1 via 10.10.10.6
valid cached adjacency
tag rewrite with Se0/1.1, point2point, tags imposed: {20 30}

The following section of the output provides information about the second adjacency. For the second adjacency, no tag rewrite occurs as indicated by the entry "tag rewrite with , ," and MPLS tags are not imposed on the packet indicated by the entry "tags imposed : {}." The router also discards this packet indicated by the entry "valid discard adjacency."

Example:

192.168.4.0/24, version 6, attached, connected
0 packets, 0 bytes
tag information set
local tag: 28
via Loopback102, 0 dependencies
valid discard adjacency
tag rewrite with , , tags imposed: {}
192.168.4.0/32, version 4, receive
192.168.4.1/32, version 3, receive
192.168.4.255/32, version 5, receive
192.168.0.0/24, version 2, receive
255.255.255.255/32, version 1, receive

Step 3

exit

Use this command to exit to user EXEC mode. For example:

Example:

Router# exit
Router>

Configuration Examples for Basic CEF

There are no configuration examples for Cisco Express Forwarding. Cisco Express Forwarding is enabled by default.

Where to Go Next

If you want to disable Cisco Express Forwarding or distributed Cisco Express Forwarding operation, refer to Enabling or Disabling Cisco Express Forwarding or distributed Cisco Express Forwarding to Customize Switching/Forwarding for Dynamic Networks.

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

IP switching commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples.

Cisco IOS IP Switching Command Reference

Overview of the Cisco Express Forwarding feature

Cisco Express Forwarding Overview

Tasks for enabling or disabling Cisco Express Forwarding or distributed Cisco Express Forwarding

Enabling or Disabling Cisco Express Forwarding or distributed Cisco Express Forwarding to Customize Switching/Forwarding for Dynamic Networks

Tasks for configuring a load-balancing scheme for Cisco Express Forwarding

Configuring a Load-Balancing Scheme for Cisco Express Forwarding Traffic

Tasks for configuring Cisco Express Forwarding consistency checkers

Configuring Cisco Express Forwarding Consistency Checkers for Route Processors and Line Cards

Tasks for configuring epochs for Cisco Express Forwarding tables

Configuring Epochs to Clear and Rebuild Cisco Express Forwarding and Adjacency Tables

Tasks for configuring and verifying Cisco Express Forwarding network accounting

Configuring Cisco Express Forwarding Network Accounting

Tasks for customizing the display of recorded Cisco Express Forwarding events

Customizing the Display of Recorded Cisco Express Forwarding Events

Verification steps for Cisco Express Forwarding switching

Click Here How to Verify Cisco Express Forwarding Switching

Troubleshooting tips for incomplete adjacencies

Click Here Troubleshooting Incomplete Adjacencies with CEF

Description and use of the Cisco Express Forwarding consistency checkers available for the Cisco 7500 and 12000 series routers

Troubleshooting Prefix Inconsistencies with Cisco Express Forwarding

Information about troubleshooting Cisco Express Forwarding routing loops and suboptimal routing

Troubleshooting Cisco Express Forwarding Routing Loops

Causes of common Cisco Express Forwarding-related error messages on platforms running distributed Cisco Express Forwarding switching (Cisco 7500 series routers and Cisco 12000 Series Internet routers) and how to troubleshoot them

Troubleshooting Cisco Express Forwarding-Related Error Messages

Explanation of and troubleshooting information for the Cisco IOS software implementation of Layer 3 load balancing across multiple parallel links when Cisco Express Forwarding is used

Troubleshooting Load Balancing Over Parallel Links Using Cisco Express Forwarding

QoS features that require Cisco Express Forwarding

When Is CEF Required for Quality of Service

Standards

Standard

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

--

MIBs

MIB

MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

Click Here

RFCs

RFC

Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

--

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

Click Here

Feature Information for Basic CEF

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.

Feature Information for Configuring Basic Cisco Express Forwarding

Feature Name

Releases

Feature Configuration Information

CEF/dCEF - Cisco Express Forwarding

Cisco IOS XE Release 2.1 15.0(1)S

This feature was introduced on Cisco ASR 1000 Series Routers.

This feature was integrated into Cisco IOS Release 15.0(1)S.

Glossary

adjacency --A relationship formed between selected neighboring routers and end nodes for the purpose of exchanging routing information. Adjacency is based upon the use of a common media segment by the routers and nodes involved.

Cisco Express Forwarding --A Layer 3 switching technology. Cisco Express Forwarding can also refer to central Cisco Express Forwarding mode, one of two modes of Cisco Express Forwarding operation. Cisco Express Forwarding enables a Route Processor (RP) to perform express forwarding. Distributed Cisco Express Forwarding is the other mode of Cisco Express Forwarding operation.

distributed Cisco Express Forwarding --A type of Cisco Express Forwarding switching in which line cards (such as Versatile Interface Processor (VIP) line cards) maintain identical copies of the forwarding information base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters; this relieves the Route Switch Processor of involvement in the switching operation.

FIB --forwarding information base. A component of Cisco Express Forwarding. The router uses the FIB lookup table to make destination-based switching decisions during Cisco Express Forwarding operation. The router maintains a mirror image of the forwarding information in an IP routing table.

IPC --interprocess communication. The mechanism that enables the distribution of Cisco Express Forwarding tables from the Route Switch Processor (RSP) to the line card when the router is operating in distributed Cisco Express Forwarding mode.

label disposition --The removal of Multiprotocol Label Switching (MPLS) headers at the edge of a network. In MPLS label disposition, packets arrive on a router as MPLS packets and, with the headers removed, are transmitted as IP packets.

label imposition --The action of putting a label on a packet.

LER --label edge router. A router that performs label imposition.

LFIB --label forwarding information base. The data structure used by switching functions to switch labeled packets.

LIB --label information base. A database used by a label switch router (LSR) to store labels learned from other LSRs, as well as labels assigned by the local LSR.

line card --A general term for an interface processor that can be used in various Cisco products. For example, a Versatile Interface Processor (VIP) is a line card for the Cisco 7500 series router.

LSP --label switched path. A sequence of hops (Router 0...Router n). A packet travels from R0 to Rn by means of label switching mechanisms. An LSP can be chosen dynamically, based on normal routing mechanisms, or it can be configured manually.

LSR --label switch router. A Layer 3 router that forwards a packet based on the value of a label encapsulated in the packet.

MPLS --Multiprotocol Label Switching. An emerging industry standard for the forwarding of packets along the normal routing paths (sometimes called MPLS hop-by-hop forwarding).

prefix --The network address portion of an IP address. A prefix is specified by a network and mask and is generally represented in the format network/mask. The mask indicates which bits are the network bits. For example, 1.0.0.0/16 means that the first 16 bits of the IP address are masked, making them the network bits. The remaining bits are the host bits. In this example, the network number is 10.0.

RIB --Routing Information Base. A central repository of routes that contains Layer 3 reachability information and destination IP addresses or prefixes. The RIB is also known as the routing table.

RP --Route Processor. The processor module in the Cisco 7000 series routers that contains the CPU, system software, and most of the memory components that are used in the router. It is sometimes called a supervisory processor.

RSP --Route Switch Processor. The processor module used in the Cisco 7500 series routers that integrates the functions of the Route Processor (RP) and the Switch Processor (SP).

SP --Switch Processor. Cisco 7000 series processor module that acts as the administrator for all CxBus activities. It is also sometimes called a CiscoBus controller.

VIP --Versatile Interface Processor. An interface card used in Cisco 7000 and Cisco 7500 series routers. The VIP provides multilayer switching and runs Cisco IOS.

VPN --Virtual Private Network. The result of a router configuration that enables IP traffic to use tunneling to travel securely over a public TCP/IP network.

VRF --A Virtual Private Network (VPN) routing/forwarding instance. A VRF consists of an IP routing table, a derived forwarding table, a set of interfaces that use the forwarding table, and a set of rules and routing protocols that determine what goes into the forwarding table. In general, a VRF includes the routing information that defines a customer VPN site that is attached to a PE router.

Chapter 3. Enabling or Disabling CEF or dCEF

This module contains information about Cisco Express Forwarding and describes the required and optional tasks for enabling or disabling Cisco Express Forwarding and distributed Cisco Express Forwarding. Cisco Express Forwarding is an advanced Layer 3 IP switching technology. It optimizes network performance and scalability for all kinds of networks: those that carry small amounts of traffic and those that carry large amounts of traffic in complex patterns, such as the Internet and networks characterized by intensive web-based applications or interactive sessions.

- Finding Feature Information

- Prerequisites for Enabling or Disabling CEF or dCEF

- Restrictions for Enabling or Disabling CEF or dCEF

- Information About Enabling or Disabling CEF or dCEF

- How to Enable or Disable Central CEF or dCEF

- Configuration Examples for Central CEF or dCEF

- Additional References

- Feature Information for Enabling or Disabling CEF or dCEF

- Glossary

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to Click Here . An account on Cisco.com is not required.

Prerequisites for Enabling or Disabling CEF or dCEF

Cisco Express Forwarding requires a software image that includes Cisco Express Forwarding and IP routing enabled on the switch or router.

Restrictions for Enabling or Disabling CEF or dCEF

Central Cisco Express Forwarding or distributed Cisco Express Forwarding has the following restrictions:

- The Cisco 12000 Series Internet routers operate only in distributed Cisco Express Forwarding mode.

- If you enable Cisco Express Forwarding and then create an access list that uses the logkeyword, the packets that match the access list are not Cisco Express Forwarding switched. They are process switched. Logging disables Cisco Express Forwarding.

- Distributed Cisco Express Forwarding switching cannot be configured on the same Versatile Interface Processor (VIP) card on which distributed fast switching is configured.

- Distributed Cisco Express Forwarding is not supported on Cisco 7200 series routers.

Restrictions for Cisco Express Forwarding or Distributed Cisco Express Forwarding Operation on an Interface

- On the Cisco 12000 Series Internet Router, you must not disable distributed Cisco Express Forwarding on an interface.

- Not all switching methods are available on all platforms.

Information About Enabling or Disabling CEF or dCEF

- Cisco Platform Support for Central CEF and dCEF

- When to Enable or Disable Central CEF on a Router

- When to Enable dCEF on a Line Card

- When to Enable or Disable CEF on an Interface

Cisco Platform Support for Central CEF and dCEF

Cisco Express Forwarding is enabled by default on most Cisco platforms running Cisco IOS software Release12.0 or later. When Cisco Express Forwarding is enabled on a router, the Route Processor (RP) performs the express forwarding.

To find out if Cisco Express Forwarding is enabled on your platform, enter the show ip cefcommand. If Cisco Express Forwarding is enabled, you receive output that looks like this:

Router# show ip cef
Prefix              Next Hop            Interface
[...]
10.2.61.8/24        192.168.100.1       FastEthernet1/0/0
192.168.101.1       FastEthernet6/1
[...]

If Cisco Express Forwarding is not enabled on your platform, the output for the show ip cefcommand looks like this:

Router# show ip cef
%CEF not running

Distributed Cisco Express Forwarding is enabled by default on the Catalyst 6500 series switch, the Cisco 7500 series router, and the Cisco 12000 Series Internet Router. When distributed Cisco Express Forwarding is enabled on your platform, the line cards perform the express forwarding.

If Cisco Express Forwarding is not enabled on your platform, use the ip cefcommand to enable central Cisco Express Forwarding or the ip cef distributed command to enable distributed Cisco Express Forwarding.

When to Enable or Disable Central CEF on a Router

Enable central Cisco Express Forwarding operation when line cards are not available for Cisco Express Forwarding switching or when you need to use features not compatible with distributed Cisco Express Forwarding switching. When central Cisco Express Forwarding operation is enabled, the Cisco Express Forwarding Forwarding Information Base (FIB) and adjacency tables reside on the RP, and the RP performs express forwarding.

Disable central Cisco Express Forwarding on a router when you want to turn off central Cisco Express Forwarding on the router and on all interfaces on the router. You might want to do this if your router and router interfaces are configured with a feature that central Cisco Express Forwarding or distributed Cisco Express Forwarding does not support.

To disable central Cisco Express Forwarding on a router and on all interfaces on the router, use the no ip cef command.

When to Enable dCEF on a Line Card

Enable distributed Cisco Express Forwarding on a line card when you want the line card to perform express forwarding so that the RP can handle routing protocols or switch packets from legacy interface processors. When distributed Cisco Express Forwarding is enabled, line cards, such as the VIP line cards or the Cisco 12000 Series Internet Router line cards, maintain an identical copy of the FIB and adjacency tables. The line cards perform express forwarding between port adapters, thus relieving the RP of involvement in the switching operation. distributed Cisco Express Forwarding uses an interprocess communication (IPC) mechanism to ensure synchronization of FIB tables and adjacency tables on the RP and line cards.

The Cisco 12000 Series Internet routers operate only in distributed Cisco Express Forwarding mode. In other routers you can mix various types of line cards in the same router, and all of the line cards you are using need not support Cisco Express Forwarding. When a line card that does not support Cisco Express Forwarding receives a packet, the line card forwards the packet to the next higher switching layer (the RP) or forwards the packet to the next hop for processing. This structure allows legacy interface processors to exist in the router with newer interface processors.

Note

When you enable distributed Cisco Express Forwarding globally, all interfaces that support distributed Cisco Express Forwarding are enabled by default.

When to Enable or Disable CEF on an Interface

You need to decide whether or not you want Cisco Express Forwarding operation on an interface. In some instances, you might want to disable Cisco Express Forwarding or distributed Cisco Express Forwarding on a particular interface because that interface is configured with a feature that Cisco Express Forwarding or distributed Cisco Express Forwarding does not support. Because all interfaces that support Cisco Express Forwarding or distributed Cisco Express Forwarding are enabled by default when you enable Cisco Express Forwarding operation globally, you must use the no form of the ip route-cache cefcommand to turn off Cisco Express Forwarding operation on a particular interface. To reenable Cisco Express Forwarding, use the ip route-cache cef command. To reenable distributed Cisco Express Forwarding, use the ip route-cache distributed command.

Disabling Cisco Express Forwarding or distributed Cisco Express Forwarding on an interface disables Cisco Express Forwarding switching for packets forwarded to the interface, but has no effect on packets forwarded out of the interface.

When you disable Cisco Express Forwarding or distributed Cisco Express Forwarding, Cisco IOS software switches packets received on the interface using the next fastest switching path. For Cisco Express Forwarding, the next fastest switching path is fast switching on the RP. For distributed Cisco Express Forwarding, the next fastest switching path is Cisco Express Forwarding on the RP.

The input interface determines the Cisco IOS switching path that a packet takes. Consider the following rules of thumb when enabling or disabling switching methods on a particular interface:

- You need Cisco Express Forwarding to be enabled on the incoming interface for packets to be Cisco Express Forwarding switched.

- Because Cisco Express Forwarding makes the forwarding decision on input, you need to use the no ip route-cache cefcommand on the ingress interface if you want to disable Cisco Express Forwarding.

- In contrast, because Cisco IOS builds a fast-switching cache entry after switching a packet, a packet coming in on a process-switched interface and going out through a fast-switched interface is fast switched.

- If you want to disable fast switching, use the no ip route-cache command on the egress interface.

How to Enable or Disable Central CEF or dCEF

To enable or disable Cisco Express Forwarding or distributed Cisco Express Forwarding, perform either of the following tasks depending on whether you want to enable or disable Cisco Express Forwarding or distributed Cisco Express Forwarding on the router or to enable or disable Cisco Express Forwarding or distributed Cisco Express Forwarding on an interface:

- Enabling or Disabling CEF or dCEF on a Router

- Enabling or Disabling CEF or dCEF on an Interface

Enabling or Disabling CEF or dCEF on a Router

Perform the following task to enable or disable Cisco Express Forwarding or distributed Cisco Express Forwarding operation on a router. Cisco Express Forwarding can optimize your network performance and scalability.

SUMMARY STEPS

1.    enable

2.    show ip cef [vrf vrf-name] [unresolved [detail]] | [detail | [summary]]

3.    configure terminal

4.    Do one of the following:

- [no] ip cef

- [no] ip cef distributed

5.    exit

6.    show ip cef [vrf vrf-name] [unresolved [detail] | [detail | summary]]

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

show ip cef [vrf vrf-name] [unresolved [detail]] | [detail | [summary]]

Example:

Router# show ip cef

Displays entries in the forwarding information base (FIB).

Use this command to determine if Cisco Express Forwarding is enabled globally and on a particular interface. If Cisco Express Forwarding is not enabled, the output displays:

%CEF not running

Step 3

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 4

Do one of the following:

- [no] ip cef

- [no] ip cef distributed

Example:

Router(config)# ip cef

Example:

Example:

Router(config)# ip cef distributed

Enables Cisco Express Forwarding on the route processor card.

or

Enables distributed Cisco Express Forwarding operation. Cisco Express Forwarding information is distributed to line cards. Line cards perform express forwarding.

Step 5

exit

Example:

Router(config)# end

Exits to privileged EXEC mode.

Step 6

show ip cef [vrf vrf-name] [unresolved [detail] | [detail | summary]]

Example:

Router# show ip cef

Displays entries in the FIB.

Use this command to verify that Cisco Express Forwarding is enabled. If Cisco Express Forwarding is enabled, the output displays destination prefixes, next-hop IP addresses, and next-hop interfaces.

Enabling or Disabling CEF or dCEF on an Interface

Perform the following task to enable or disable Cisco Express Forwarding or distributed Cisco Express Forwarding operation on an interface. Cisco Express Forwarding can optimize your network performance and scalability.

SUMMARY STEPS

1.    enable

2.    show cef interface [type number] [statistics] [detail]

3.    configure terminal

4.    Do one of the following:

- interface type slot / port

- interface type slot / port-adapter / port

5.    [no] ip route-cache cef

6.    end

7.    show cef interface [type number] [statistics] [detail]

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

show cef interface [type number] [statistics] [detail]

Example:

Router# show cef interface fastethernet 1/0/0

Displays detailed Cisco Express Forwarding information for a specified interface or for all interfaces.

Look for "IP CEF switching enabled" or "IP Distributed CEF switching enabled" in the output.

Step 3

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 4

Do one of the following:

- interface type slot / port

- interface type slot / port-adapter / port

Example:

Router(config)# interface ethernet 1/1

Example:

or

Example:

Router(config)# interface fastethernet 1/0/0

Configures an interface type and enters interface configuration mode.

- The type argument specifies the type of interface to be configured.

- The slot/ argument specifies the slot number. Refer to the appropriate hardware manual for slot and port information.

- The port argument specifies the port number. Refer to the appropriate hardware manual for slot and port information.

- The port-adapter/ argument specifies the port adapter number. Refer to the appropriate hardware manual for information about port adapter compatibility.

Step 5

[no] ip route-cache cef

Example:

or

Example:

[no] ip route-cache distributed

Example:

Router(config-if)# no ip route-cache cef

Example:

or

Example:

Router(config-if)# no ip route-cache distributed

Disables Cisco Express Forwarding operation on an interface or enables Cisco Express Forwarding operation on an interface after Cisco Express Forwarding operation was disabled.

or

Disables distributed Cisco Express Forwarding operation on an interface or enables distributed Cisco Express Forwarding operation on an interface after distributed Cisco Express Forwarding operation was disabled.

Step 6

end

Example:

Router(config)# end

Exits to privileged EXEC mode.

Step 7

show cef interface [type number] [statistics] [detail]

Example:

Router# show cef interface fastethernet 1/0/0

Displays detailed Cisco Express Forwarding information for a specified interface or for all interfaces.

Verify that "IP CEF switching enabled" or "IP Distributed CEF switching enabled" is displayed in the output.

Configuration Examples for Central CEF or dCEF

- Example Enabling or Disabling CEF or dCEF on a Router

- Example Enabling or Disabling Central CEF or dCEF on an Interface

Example Enabling or Disabling CEF or dCEF on a Router

Cisco Express Forwarding is enabled by default on the Cisco 7100, 7200, and 7500 series routers. You might want to disable Cisco Express Forwarding if your router and router interfaces are configured with a feature that Cisco Express Forwarding does not support. The following example shows how to disable Cisco Express Forwarding on a router and on all interfaces on the router:

configure terminal
!
no ip cef
end

Distributed Cisco Express Forwarding is enabled by default on the Cisco 6500 and 12000 series routers. The following example shows how to enable distributed Cisco Express Forwarding on the line cards of a router, such as the Cisco 7500 series router, that supports distributed Cisco Express Forwarding:

configure terminal
!
ip cef distributed
end

You might want to disable distributed Cisco Express Forwarding if your router and router interfaces are configured with a feature that distributed Cisco Express Forwarding does not support. The following example shows how to disable distributed Cisco Express Forwarding on a router:

configure terminal
!

no ip cef distributed

end

Example Enabling or Disabling Central CEF or dCEF on an Interface

All interfaces that support Cisco Express Forwarding operation (central Cisco Express Forwarding or distributed Cisco Express Forwarding) are enabled by default when you enable Cisco Express Forwarding operation globally. You might want to disable central Cisco Express Forwarding or distributed Cisco Express Forwarding on a particular interface if that interface is configured with a feature that central Cisco Express Forwarding or distributed Cisco Express Forwarding does not support.

The following example shows how to disable central Cisco Express Forwarding on a particular interface:

configure terminal
!
interface ethernet 1/1
no ip route-cache cef
end

The following example shows how to reenable central Cisco Express Forwarding operation on an interface:

configure terminal
!
interface ethernet 1/1
ip route-cache cef
end

The following example shows how to disable distributed Cisco Express Forwarding on Ethernet interface 0:

configure terminal
!
interface e0
no ip route-cache distributed
end

The following example shows how to reenable distributed Cisco Express Forwarding operation on Ethernet interface 0:

configure terminal
!
ip cef distributed
!
interface e0
# ip route-cache distributed
end

The following example shows how to enable Cisco Express Forwarding operation on the router (globally) and turn off Cisco Express Forwarding operation on Ethernet interface 0:

configure terminal
!
ip cef
!
interface e0
no ip route-cache cef
end

The following example shows how to enable distributed Cisco Express Forwarding operation on the router (globally) and turn off Cisco Express Forwarding operation on Ethernet interface 0:

configure terminal
!
ip cef distributed
interface e0
no ip route-cache cef
end

The following example shows how to reenable distributed Cisco Express Forwarding operation on Ethernet interface 0:

configure terminal
!
ip cef distributed
!
interface e0
ip route-cache distributed
end

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

IP switching commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples.

Cisco IOS IP Switching Command Reference

Overview of the Cisco Express Forwarding feature

Cisco Express Forwarding Overview

Tasks for verifying Cisco Express Forwarding information on your router

Configuring Basic Cisco Express Forwarding for Improved Performance, Scalability, and Resiliency in Dynamic Networks

Tasks for configuring a load-balancing scheme for Cisco Express Forwarding

Configuring a Load-Balancing Scheme for Cisco Express Forwarding Traffic

Tasks for configuring Cisco Express Forwarding consistency checkers

Configuring Cisco Express Forwarding Consistency Checkers for Route Processors and Line Cards

Tasks for configuring epochs for Cisco Express Forwarding tables

Configuring Epochs to Clear and Rebuild Cisco Express Forwarding and Adjacency Tables

Tasks for configuring and verifying Cisco Express Forwarding network accounting

Configuring Cisco Express Forwarding Network Accounting

Tasks for customizing the display of recorded Cisco Express Forwarding events

Customizing the Display of Recorded Cisco Express Forwarding Events

Troubleshooting tips for incomplete adjacencies

Click Here Troubleshooting Incomplete Adjacencies with CEF

Description and use of the Cisco Express Forwarding consistency checkers available for the Cisco 7500 and 12000 series routers

Troubleshooting Prefix Inconsistencies with Cisco Express Forwarding

Information about troubleshooting Cisco Express Forwarding routing loops and suboptimal routing

Troubleshooting Cisco Express Forwarding Routing Loops

Causes of common Cisco Express Forwarding-related error messages on platforms running distributed Cisco Express Forwarding switching (Cisco 7500 series routers and Cisco 12000 Series Internet routers) and how to troubleshoot them

Troubleshooting Cisco Express Forwarding-Related Error Messages

Explanation of and troubleshooting information for the Cisco IOS software implementation of Layer 3 load balancing across multiple parallel links when Cisco Express Forwarding is used

Troubleshooting Load Balancing Over Parallel Links Using Cisco Express Forwarding

QoS features that require Cisco Express Forwarding

When Is CEF Required for Quality of Service

Cisco Express Forwarding command changes for MPLS HA application and the MFI infrastructure in Cisco IOS 12.2S releases

Cisco Express Forwarding: Command Changes

Standards

Standard

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

--

MIBs

MIB

MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

Click Here

RFCs

RFC

Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

--

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

Click Here

Feature Information for Enabling or Disabling CEF or dCEF

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.

Feature Information for Enabling or Disabling Cisco Express Forwarding or Distributed Cisco Express Forwarding

Feature Name

Releases

Feature Configuration Information

This table is intentionally left blank because no features were introduced or modified in Cisco IOS Release 12.2(1) or later. This table will be updated when feature information is added to this module.

--

--

Glossary

adjacency --A relationship formed between selected neighboring routers and end nodes for the purpose of exchanging routing information. Adjacency is based upon the use of a common media segment by the routers and nodes involved.

Cisco Express Forwarding --A Layer 3 switching technology. Cisco Express Forwarding can also refer to central Cisco Express Forwarding mode, one of two modes of Cisco Express Forwarding operation. Cisco Express Forwarding enables a Route Processor to perform express forwarding. Distributed Cisco Express Forwarding is the other mode of Cisco Express Forwarding operation.

distributed Cisco Express Forwarding --A mode of Cisco Express Forwarding operation in which line cards (such as Versatile Interface Processor (VIP) line cards) maintain identical copies of the forwarding information base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters; this relieves the Route Switch Processor of involvement in the switching operation.

FIB --forwarding information base. A component of Cisco Express Forwarding that is conceptually similar to a routing table or information base. The router uses the FIB lookup table to make destination-based switching decisions during Cisco Express Forwarding operation. The router maintains a mirror image of the forwarding information in an IP routing table.

GRE --generic routing encapsulation. A tunneling protocol developed by Cisco that enables encapsulation of a wide variety of protocol packet types inside IP tunnels. GRE creates a virtual point-to-point link to Cisco routers at remote points over an IP internetwork. By connecting multiprotocol subnetworks in a single-protocol backbone environment, IP tunneling using GRE allows the expansion of a network across a single-protocol backbone environment.

IPC --interprocess communication. The mechanism that enables the distribution of Cisco Express Forwarding tables from the Route Switch Processor (RSP) to the line card when the router is operating in distributed Cisco Express Forwarding mode.

label disposition --The removal of Multiprotocol Label Switching (MPLS) headers at the edge of a network. In MPLS label disposition, packets arrive on a router as MPLS packets and, with the header removed, are transmitted as IP packets.

label imposition --The action of putting a label on a packet.

LER --label edge router. A router that performs label imposition.

LFIB --Label Forwarding Information Base. The data structure used by switching functions to switch labeled packets.

LIB --Label information base. A database used by a label switch router (LSR) to store labels learned from other LSRs, as well as labels assigned by the local LSR.

line card --A general term for an interface processor that can be used in various Cisco products. For example, a Versatile Interface Processor (VIP) is a line card for the Cisco 7500 series router.

LSP --label switched path. A sequence of hops (Router 0...Router n). A packet travels from R0 to Rn by means of label switching mechanisms. An LSP can be chosen dynamically, based on normal routing mechanisms, or you can configure the LSP manually.

LSR --label switch router. A Layer 3 router that forwards a packet based on the value of a label encapsulated in the packet.

MPLS --Multiprotocol Label Switching. An emerging industry standard for the forwarding of packets along the normal routing paths (sometimes called MPLS hop-by-hop forwarding).

prefix --The network address portion of an IP address. A prefix is specified by a network and mask and is generally represented in the format network/mask. The mask indicates which bits are the network bits. For example, 1.0.0.0/16 means that the first 16 bits of the IP address are masked, making them the network bits. The remaining bits are the host bits. In this example, the network number is 10.0.

RIB --Routing Information Base. A central repository of routes that contains Layer 3 reachability information and destination IP addresses or prefixes. The RIB is also known as the routing table.

RP --Route Processor. The processor module in the Cisco 7000 series routers that contains the CPU, system software, and most of the memory components that are used in the router. It is sometimes called a supervisory processor.

RSP --Route Switch Processor. The processor module used in the Cisco 7500 series routers that integrates the functions of the Route Processor (RP) and the Switch Processor (SP).

SP --Switch Processor. Cisco 7000-series processor module that acts as the administrator for all CxBus activities. It is also sometimes called a CiscoBus controller.

VIP --Versatile Interface Processor. An interface card used in Cisco 7000 and Cisco 7500 series routers. The VIP provides multilayer switching and runs Cisco IOS software.

VPN --Virtual Private Network. The result of a router configuration that enables IP traffic to use tunneling to travel securely over a public TCP/IP network.

VRF --A Virtual Private Network (VPN) routing/forwarding instance. A VRF consists of an IP routing table, a derived forwarding table, a set of interfaces that use the forwarding table, and a set of rules and routing protocols that determine what goes into the forwarding table. In general, a VRF includes the routing information that defines a customer VPN site that is attached to a PE router.

Chapter 4. Configuring a Load-Balancing Scheme

This module contains information about Cisco Express Forwarding and describes the tasks for configuring a load-balancing scheme for Cisco Express Forwarding traffic. Load-balancing allows you to optimize resources by distributing traffic over multiple paths.

Cisco Express Forwarding is an advanced Layer 3 IP switching technology. It optimizes network performance and scalability for all kinds of networks: those that carry small amounts of traffic and those that carry large amounts of traffic in complex patterns, such as the Internet and networks characterized by intensive web-based applications or interactive sessions.

- Finding Feature Information

- Prerequisites for a Load-Balancing Scheme

- Restrictions for a Load-Balancing Scheme

- Information About a Load-Balancing Scheme

- How to Configure a Load-Balancing Scheme

- Configuration Examples for a Load-Balancing Scheme

- Additional References

- Feature Information for a Load-Balancing Scheme

- Glossary

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to Click Here . An account on Cisco.com is not required.

Prerequisites for a Load-Balancing Scheme

- Cisco Express Forwarding or distributed Cisco Express Forwarding must be enabled on your switch or router.

- If you enable per-packet load balancing for traffic going to a particular destination, all interfaces that can forward traffic to that destination must be enabled for per-packet load balancing.

Restrictions for a Load-Balancing Scheme

You must globally configure load balancing on Cisco 12000 Series Router E2 line cards in the same way: either in per-destination or per-packet mode. It is not possible (as in other Cisco IOS software-based platforms) to configure some packet prefixes in per-destination mode and others in per-packet mode.

Information About a Load-Balancing Scheme

- Cisco Platform Support for Central CEF and dCEF

- CEF Load-Balancing Overview

- Per-Destination Load Balancing

- Per-Packet Load Balancing

- Load-Balancing Algorithms

Cisco Platform Support for Central CEF and dCEF

Cisco Express Forwarding is enabled by default on most Cisco platforms running Cisco IOS software Release 12.0 or later. When Cisco Express Forwarding is enabled on a router, the Route Processor (RP) performs the express forwarding.

To find out if Cisco Express Forwarding is enabled on your platform, enter the show ip cefcommand. If Cisco Express Forwarding is enabled, you receive output that looks like this:

Router# show ip cef
Prefix              Next Hop            Interface
[...]
10.2.61.8/24        192.168.100.1       FastEthernet1/0/0
192.168.101.1       FastEthernet6/1
[...]

If Cisco Express Forwarding is not enabled on your platform, the output for the show ip cefcommand looks like this:

Router# show ip cef
%CEF not running

Distributed Cisco Express Forwarding is enabled by default on the Catalyst 6500 series switch, the Cisco 7500 series router, and the Cisco 12000 series router. When distributed Cisco Express Forwarding is enabled on your platform, the line cards perform the express forwarding.

If Cisco Express Forwarding is not enabled on your platform, use the ip cefcommand to enable (central) Cisco Express Forwarding or the ip cef distributed command to enable distributed Cisco Express Forwarding.

CEF Load-Balancing Overview

Cisco Express Forwarding load balancing is based on a combination of source and destination packet information; it allows you to optimize resources by distributing traffic over multiple paths.

You can configure load balancing on a per-destination or per-packet basis. Because load-balancing decisions are made on the outbound interface, load balancing must be configured on the outbound interface.

Per-Destination Load Balancing

Per-destination load balancing allows the router to use multiple paths to achieve load sharing across multiple source-destination host pairs. Packets for a given source-destination host pair are guaranteed to take the same path, even if multiple paths are available. Traffic streams destined for different pairs tend to take different paths.

Per-destination load balancing is enabled by default when you enable Cisco Express Forwarding. To use per-destination load balancing, you do not perform any additional tasks once Cisco Express Forwarding is enabled. Per-destination is the load-balancing method of choice for most situations.

Because per-destination load balancing depends on the statistical distribution of traffic, load sharing becomes more effective as the number of source-destination host pairs increases.

You can use per-destination load balancing to ensure that packets for a given host pair arrive in order. All packets intended for a certain host pair are routed over the same link (or links).

Typically, you disable per-destination load balancing when you want to enable per-packet load balancing.

Note

The Cisco 10000 series router and the Cisco 12000 series router are configured by default to perform per-destination load balancing.

Per-Packet Load Balancing

Cisco Express Forwarding Per-packet load balancing allows the router to send successive data packets over different paths without regard to individual hosts or user sessions. It uses the round-robin method to determine which path each packet takes to the destination. Per-packet load balancing ensures that the traffic is balanced over multiple links.

Per-packet load balancing is good for single-path destinations, but packets for a given source-destination host pair might take different paths. Per-packet load balancing can therefore introduce reordering of packets. This type of load balancing is inappropriate for certain types of data traffic (such as voice traffic over IP) that depend on packets arriving at the destination in sequence.

Use per-packet load balancing to help ensure that a path for a single source-destination host pair does not get overloaded. If the bulk of the data passing through parallel links is for a single pair, per-destination load balancing overloads a single link while other links have very little traffic. Enabling per-packet load balancing allows you to use alternate paths to the same busy destination.

Note

Although per-packet load balancing is intended for use on the majority of Cisco IOS routers, it is not supported on the Cisco ASR 1000 (and higher) Series Aggregation Services Router. Also, per-packet load balancing can result in out-of-sequence (OOS) packet delivery errors on some routers, which can cause applications such as VoIP to malfunction. Therefore, per-packet load balancing is not recommended. For more information, see the release notes and caveats for your platform and software release.

Load-Balancing Algorithms

The following load-balancing algorithms are provided for use with Cisco Express Forwarding traffic. You select a load-balancing algorithm with the ip cef load-sharing algorithm command.

- Original algorithm--The original Cisco Express Forwarding load-balancing algorithm produces distortions in load sharing across multiple routers because the same algorithm was used on every router. Depending on your network environment, you should select either the universal algorithm (default) or the tunnel algorithm instead.

- Universal algorithm--The universal load-balancing algorithm allows each router on the network to make a different load sharing decision for each source-destination address pair, which resolves load-sharing imbalances. The router is set to perform universal load sharing by default.

- Tunnel algorithm--The tunnel algorithm is designed to balance the per-packet load when only a few source and destination pairs are involved.

- Include-ports algorithm--The include-ports algorithm allows you to use the Layer 4 source and destination ports as part of the load-balancing decision. This method benefits traffic streams running over equal cost paths that are not load shared because the majority of the traffic is between peer addresses that use different port numbers, such as Real-Time Protocol (RTP) streams. The include-ports algorithm is available in Cisco IOS Release 12.4(11)T and later releases.

- GTP-U TEID-Based ECMP Load-Balancing Algorithm for Cisco IOS XE Software

GTP-U TEID-Based ECMP Load-Balancing Algorithm for Cisco IOS XE Software

GPRS Tunneling Protocol (GTP) is mainly used to deliver mobile data on wireless networks via the Cisco ASR 1000 Series Aggregation Services Routers as the core router. When two routers carrying GTP traffic are connected with equal-cost multi-path (ECMP) routing between them, you can use the show ip cef exact-route source - ip address [src-port port number] destination-ip address[ dest-port port number] [ gtp-teid teid] command in the User EXEC mode or the Privileged EXEC mode to verify the interface selected for load balancing.

To achieve load balancing, the Cisco ASR 1000 Series Aggregation Services Routers use a 4-tuple source IP address, destination IP address, L4 source and destination port (if traffic is TCP or UDP), and fields from the packet. However, for GTP traffic, the presence of limited number of unique values for these fields restricts the equal distribution of traffic load on the tunnel. To avoid polarization for GTP traffic in load balancing, a tunnel endpoint identifier (TEID) in the GTP header is used instead of the UDP port number. Because TEID is unique per tunnel, traffic can be evenly load balanced across ECMPs. This feature allows you to look inside the GTP header and balance the traffic over ECMP on a per subscriber basis.

The GTP-U TEID-Based ECMP Load-Balancing Algorithm feature adds support for:

- GTP with IPv4 and IPv6 transport header on physical interface

- GTP traffic over the Traffic Engineering (TE) tunnel, which supports load balancing between different TE tunnels

- GTPv1-U with UDP port 2152

- Up to 8 ECMP paths

- Restrictions for GTP-U TEID-Based ECMP Load-Balancing Algorithm

- Enabling the GTP-U TEID Load-Balancing Algorithm

Restrictions for GTP-U TEID-Based ECMP Load-Balancing Algorithm

The following restrictions apply to the GTP-U TEID-Based ECMP Load-Balancing Algorithm feature:

- GTPv0 is not supported to avoid extra performance impact.

- GTP-C and GTP over L2VPN are not supported.

Enabling the GTP-U TEID Load-Balancing Algorithm

Use the ip cef load-sharing algorithm include-ports source destination gtp command to enable the GTP-U TEID load-balancing algorithm for IPv4.

Use the ipv6 cef load-sharing algorithm include-ports source destination gtp command to enable the GTP-U TEID load-balancing algorithm for IPv6.

Use the show ip cef exact-route source - ip address [src-port port number] destination-ip address [dest-port port number] [ gtp-teid teid] command to display the exact route of GTP-U TEID for IPv4.

Use the show ipv6 cef exact-route source-ip address [src-port port number] destination-ip address [dest-port port number] [gtp-teid teid] command to display the exact route of GTP-U TEID for IPv6.

How to Configure a Load-Balancing Scheme

- Enabling or Disabling Per-Destination Load Balancing

- Configuring Per-Packet Load Balancing

- Selecting a Tunnel Load-Balancing Algorithm

- Selecting an Include-Ports Layer 4 Load-Balancing Algorithm

Enabling or Disabling Per-Destination Load Balancing

Perform this task to enable or disable Cisco Express Forwarding per-destination load balancing.

Typically, you disable per-destination load balancing when you want to enable per-packet load balancing.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    Do one of the following:

- interface type slot / port

- interface type slot / port-adapter / port

4.    [no] ip load-sharing per-destination

5.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

Do one of the following:

- interface type slot / port

- interface type slot / port-adapter / port

Example:

Router(config)# interface ethernet 1/1

Example:

or

Example:

Router(config)# interface fastethernet 1/0/0

Configures an interface type and enters interface configuration mode.

- The type argument specifies the type of interface to be configured.

- The slot argument specifies the slot number. Refer to the appropriate hardware manual for slot and port information.

- The port argument specifies the port number. Refer to the appropriate hardware manual for slot and port information.

- The port-adapterargument specifies the port adapter number. Refer to the appropriate hardware manual for information about port adapter compatibility.

Note:
The slashes after the slotargument and port-adapterargument are required.

Step 4

[no] ip load-sharing per-destination

Example:

Router(config-if)# no ip load-sharing per-destination

Enables per-destination load balancing for Cisco Express Forwarding on the interface.

Note:
The no ip load-sharing command disables load balancing for Cisco Express Forwarding on the interface.

Step 5

end

Example:

Router(config-if)# end

Exits to privileged EXEC mode.

Configuring Per-Packet Load Balancing

Perform the following task to configure Cisco Express Forwarding per-packet load balancing.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    Do one of the following:

- interface type slot / port

- interface type slot / port-adapter / port

4.    ip load-sharing per-packet

5.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

Do one of the following:

- interface type slot / port

- interface type slot / port-adapter / port

Example:

Router(config)# interface ethernet 1/1

Example:

or

Example:

Router(config)# interface fastethernet 1/0/0

Configures an interface type and enters interface configuration mode.

- The type argument specifies the type of interface to be configured.

- The slotargument specifies the slot number. Refer to the appropriate hardware manual for slot and port information.

- The port argument specifies the port number. Refer to the appropriate hardware manual for slot and port information.

- The port-adapterargument specifies the port adapter number. Refer to the appropriate hardware manual for information about port adapters.

Note:
The slashes after the slotargument and port-adapterargument are required.

Step 4

ip load-sharing per-packet

Example:

Router(config-if)# ip load-sharing per-packet

Enables per-packet load balancing for Cisco Express Forwarding on the interface.

Step 5

end

Example:

Router(config-if)# end

Exits to privileged EXEC mode.

Selecting a Tunnel Load-Balancing Algorithm

Perform the following task to select a tunnel load-balancing algorithm for Cisco Express Forwarding traffic. Select the tunnel algorithm when your network environment contains only a few source and destination pairs.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ip cef load-sharing algorithm {original | tunnel [id] | universal [id] | include-ports {source[id]| [destination] [id] | source[id] destination [id]}}

4.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

ip cef load-sharing algorithm {original | tunnel [id] | universal [id] | include-ports {source[id]| [destination] [id] | source[id] destination [id]}}

Example:

Router(config)# ip cef load-sharing algorithm tunnel

Selects a Cisco Express Forwarding load-balancing algorithm.

- The original keyword sets the load-balancing algorithm to the original algorithm, based on a source and destination hash.

- The tunnel keyword sets the load-balancing algorithm to one that can be used in tunnel environments or in environments where there are only a few IP source and destination address pairs.

- The id argument is a fixed identifier.

- The universal keyword sets the load-balancing algorithm to one that uses a source and destination and an ID hash.

- The include-ports source keywords set the load-balancing algorithm to one that uses the source port.

- The include-ports destination keywords set the load-balancing algorithm to one that uses the destination port.

- The include-ports source destinationkeywords set the load-balancing algorithm to one that uses both source and destination ports.

Step 4

end

Example:

Router(config)# end

Exits to privileged EXEC mode.

Selecting an Include-Ports Layer 4 Load-Balancing Algorithm

Perform the following task to select an include-ports load-balancing algorithm for Cisco Express Forwarding traffic. Select the include-port algorithm when your network environment contains traffic running over equal-cost paths that is not load shared because the majority of the traffic is between peer addresses with different port numbers, such as RTP streams.

Before You Begin

Your system must be using an image that supports Cisco Express Forwarding in Cisco IOS Release 12.4(11)T or a later release.

Note

The Layer 4 load-balancing algorithm applies to software switched packets.

For platforms that switch traffic using a hardware forwarding engine, the hardware load-balancing decision might be different from the software load-balancing decision for the same traffic stream. You might want to override the configured algorithm.

>

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ip cef load-sharing algorithm {original | tunnel [id] | universal [id] include-ports {source[id] | [destination] [id] | source[id] destination [id]}}

4.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

ip cef load-sharing algorithm {original | tunnel [id] | universal [id] include-ports {source[id] | [destination] [id] | source[id] destination [id]}}

Example:

Router(config)# ip cef load-sharing algorithm include-ports source destination

Selects a Cisco Express Forwarding load-balancing algorithm.

- The original keyword sets the load-balancing algorithm to the original algorithm, based on a source and destination hash.

- The tunnel keyword sets the load-balancing algorithm to one that can be used in tunnel environments or in environments where there are only a few IP source and destination address pairs.

- The id argument is a fixed identifier.

- The universal keyword sets the load-balancing algorithm to one that uses a source and destination and an ID hash.

- The include-ports source keyword sets the load-balancing algorithm to one that uses the source port.

- The include-ports destination keyword sets the load-balancing algorithm to one that uses the destination port.

- The include-ports source destination keyword sets the load-balancing algorithm to one that uses the source and destination ports.

Step 4

end

Example:

Router(config)# end

Exits to privileged mode.

Configuration Examples for a Load-Balancing Scheme

- Example Enabling or Disabling Per-Destination Load Balancing

- Example Configuring Per-Packet Load Balancing

- Example Selecting a Tunnel Load-Balancing Algorithm

- Example Selecting an Include-Ports Layer 4 Load-Balancing Algorithm

Example Enabling or Disabling Per-Destination Load Balancing

Per-destination load balancing is enabled by default when you enable Cisco Express Forwarding. Typically, you disable per-destination load balancing when you want to enable per-packet load balancing. The following example shows how to disable per-destination load balancing:

configure terminal

!

interface ethernet 1/1

no ip load-sharing per-destination
end

Example Configuring Per-Packet Load Balancing

The following example shows how to configure per-packet load balancing for Cisco Express Forwarding:

configure terminal
!

interface ethernet 1/1

ip load-sharing per-packet
end

If you want to enable per-packet load balancing for traffic intended for a particular destination, all interfaces that can forward traffic to that destination must be enabled for per-packet load-balancing.

Example Selecting a Tunnel Load-Balancing Algorithm

The following example shows how to select a tunnel load-balancing algorithm for Cisco Express Forwarding:

configure terminal
!

ip cef load-sharing algorithm tunnel

end

The following example shows how to disable the tunnel load-balancing algorithm:

configure terminal
!

no ip cef load-sharing algorithm tunnel

end

Example Selecting an Include-Ports Layer 4 Load-Balancing Algorithm

The following example shows how to select an include-ports Layer 4 load-balancing algorithm for Cisco Express Forwarding traffic:

configure terminal
!

ip cef load-sharing algorithm include-ports source

end

This example sets up load sharing that includes the source port in the load-balancing decision.

To disable the include-ports Layer 4 load-balancing algorithm and return to the default universal mode, enter the following commands:

configure terminal
!

no ip cef load-sharing algorithm

end

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

IP switching commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples.

Cisco IOS IP Switching Command Reference

Overview of the Cisco Express Forwarding feature

Cisco Express Forwarding Overview

Tasks for verifying basic Cisco Express Forwarding and distributed Cisco Express Forwarding operation

Configuring Basic Cisco Express Forwarding for Improved Performance, Scalability, and Resiliency in Dynamic Networks

Tasks for enabling or disabling Cisco Express Forwarding or distributed Cisco Express Forwarding

Enabling or Disabling Cisco Express Forwarding or Distributed Cisco Express Forwarding to Customize Switching and Forwarding for Dynamic Network

Tasks for configuring Cisco Express Forwarding consistency checkers

Configuring Cisco Express Forwarding Consistency Checkers for Route Processors and Line Cards

Tasks for configuring epochs for Cisco Express Forwarding tables

Configuring Epochs to Clear and Rebuild Cisco Express Forwarding and Adjacency Tables

Tasks for configuring and verifying Cisco Express Forwarding network accounting

Configuring Cisco Express Forwarding Network Accounting

Tasks for customizing the display of recorded Cisco Express Forwarding events

Customizing the Display of Recorded Cisco Express Forwarding Events

Explanation of and troubleshooting information for the Cisco IOS software implementation of Layer 3 load balancing across multiple parallel links when Cisco Express Forwarding is used

Troubleshooting Load Balancing Over Parallel Links Using Cisco Express Forwarding

Standards

Standard

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

--

MIBs

MIB

MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

Click Here

RFCs

RFC

Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

--

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

Click Here

Feature Information for a Load-Balancing Scheme

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.

Feature Information for Configuring a Load-Balancing Scheme for Cisco Express Forwarding Traffic

Feature Name

Releases

Feature Configuration Information

Cisco Express Forwarding Support for Layer 4 Port-Based Load Balancing

12.4(11)T

This feature allows Cisco Express Forwarding (CEF) to include Layer 4 port information in the decision for load sharing on paths.

In 12.4(11)T, this feature was introduced.

The following commands were modified by this feature: ip cef load-sharing algorithm and show ip cef exact-route.

GTP-U TEID-Based ECMP Load-Balancing Algorithm for Cisco IOS XE Software

Cisco IOS XE Release 3.10S

This feature allows CEF to use the GPRS Tunneling Protocol Tunnel Endpoint Identifier (GTP TEID) load-balancing algorithm.

Glossary

adjacency --A relationship formed between selected neighboring routers and end nodes for the purpose of exchanging routing information. Adjacency is based upon the use of a common media segment by the routers and nodes involved.

Cisco Express Forwarding --A Layer 3 switching technology. Cisco Express Forwarding can also refer to central Cisco Express Forwarding mode, one of two modes of Cisco Express Forwarding operation. Cisco Express Forwarding enables a Route Processor to perform express forwarding. Distributed Cisco Express Forwarding is the other mode of Cisco Express Forwarding operation.

distributed Cisco Express Forwarding --A mode of Cisco Express Forwarding operation in which line cards (such as Versatile Interface Processor [VIP] line cards) maintain identical copies of the forwarding information base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters; this relieves the Route Switch Processor of involvement in the switching operation.

FIB --forwarding information base. A component of Cisco Express Forwarding that is conceptually similar to a routing table or information base. The router uses the FIB lookup table to make destination-based switching decisions during Cisco Express Forwarding operation. The router maintains a mirror image of the forwarding information in an IP routing table.

LSP --label switched path. A sequence of hops (Router 0...Router n). A packet travels from R0 to Rn by means of label switching mechanisms. An LSP can be chosen dynamically, based on normal routing mechanisms, or you can configure the LSP manually.

prefix --The network address portion of an IP address. A prefix is specified by a network and mask and is generally represented in the format network/mask. The mask indicates which bits are the network bits. For example, 1.0.0.0/16 means that the first 16 bits of the IP address are masked, making them the network bits. The remaining bits are the host bits. In this example, the network number is 10.0.

RIB --Routing Information Base. A central repository of routes that contains Layer 3 reachability.

Chapter 5. Configuring Epochs

This document contains information about and instructions for configuring epochs for Cisco Express Forwarding tables. You can use this functionality to clear and rebuild Cisco Express Forwarding tables for consistency purposes without the loss of table information.

Cisco Express Forwarding is an advanced Layer 3 IP switching technology. It optimizes network performance and scalability for all kinds of networks: those that carry small amounts of traffic and those that carry large amounts of traffic in complex patterns, such as the Internet and networks characterized by intensive web-based applications or interactive sessions.

- Finding Feature Information

- Prerequisites for Epochs for CEF Tables

- Information About About Epochs for CEF Tables

- How to Configure Epochs

- Configuration Examples for Epochs

- Additional References

- Feature Information for Configuring Epochs

- Glossary

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to Click Here . An account on Cisco.com is not required.

Prerequisites for Epochs for CEF Tables

Cisco Express Forwarding must be up and running on the router or switch for you to configure epochs for Cisco Express Forwarding Forwarding Information Base (FIB) and adjacency tables.

Information About About Epochs for CEF Tables

Tasks for configuring epochs for Cisco Express Forwarding Forwarding Information Base (FIB) tables were introduced with the Nonstop Forwarding Enhanced FIB Refresh feature in Cisco IOS Release 12.2(8)T.

Before you configure epochs for Cisco Express Forwarding tables, you should understand the following:

(See the Nonstop Forwarding Enhanced FIB Refresh for an explanation of the term "epoch.")

Tasks for configuring epochs for Cisco Express Forwarding tables were introduced with the Nonstop Forwarding Enhanced FIB Refresh feature in Cisco IOS Release 12.2(8)T.

For links to information about other Cisco Express Forwarding and distributed Cisco Express Forwarding features you can configure, refer to the Additional References.

- Cisco Platform Support for Central CEF and dCEF

- Nonstop Forwarding Enhanced FIB Refresh

- Epoch Numbering for CEF FIB and Adjacency Tables

- Epoch Synchronization Between the RP and Line Cards

- Epoch Numbering for Routers That Support HA

- When to Refresh the CEF or Adjacency Tables

Cisco Platform Support for Central CEF and dCEF

Cisco Express Forwarding is enabled by default on most Cisco platforms running Cisco IOS software Release 12.0 or later. When Cisco Express Forwarding is enabled on a router, the Route Processor (RP) performs the express forwarding.

To find out if Cisco Express Forwarding is enabled on your platform, enter the show ip cefcommand. If Cisco Express Forwarding is enabled, you receive output that looks like this:

Router# show ip cef
Prefix              Next Hop            Interface
[...]
10.2.61.8/24        192.168.100.1       FastEthernet1/0/0
192.168.101.1       FastEthernet6/1
[...]

If Cisco Express Forwarding is not enabled on your platform, the output for the show ip cefcommand looks like this:

Router# show ip cef
%CEF not running

Distributed Cisco Express Forwarding is enabled by default on the Catalyst 6500 series switch, the Cisco 7500 series router, and the Cisco 12000 Series Internet Router. When Distributed Cisco Express Forwarding is enabled on your platform, the line cards perform the express forwarding.

If Cisco Express Forwarding is not enabled on your platform, use the ip cefcommand to enable (central) Cisco Express Forwarding or the ip cef distributed command to enable Distributed Cisco Express Forwarding.

Nonstop Forwarding Enhanced FIB Refresh

Networks must be configured to minimize traffic disruption and offer the most uptime possible. The Nonstop Forwarding (NSF) Enhanced FIB Refresh feature (included with Cisco IOS Release 12.2(8)T) enables users to continue forwarding IP traffic while Cisco Express Forwarding database tables are being rebuilt. IP forwarding on the router is therefore uninterrupted.

NSF Enhanced FIB Refresh provides for the continuation of Cisco Express Forwarding forwarding by tracking epochs. The term "epoch" refers to a period of time. A new epoch for a Cisco Express Forwarding table begins when a table rebuild is initiated. The time after this instant is in an epoch different from the time before, and the different epochs are numbered between 0 and 255. Through the use of epochs, the software can distinguish between old and new forwarding information in the same database structure and can retain the old Cisco Express Forwarding database table while the software builds a new table. This is called epoch tracking and it allows Cisco Express Forwarding forwarding to continue uninterrupted while new Cisco Express Forwarding tables are being constructed, and it makes possible a seamless switchover when the new table becomes active.

Epoch Numbering for CEF FIB and Adjacency Tables

A new epoch for a Cisco Express Forwarding table begins when a table rebuild is initiated. The time after this instant is in an epoch different from the time before. The first epoch is numbered 0, and it begins when the Cisco Express Forwarding table is created. The epoch number increases by 1 for each new revision of the Cisco Express Forwarding table until the epoch number reaches 255. The next epoch after 255 is 0. A new epoch cannot begin if any table entries remain from the last time the epoch number was used. The epoch number for a given table is the same for each instance of the table (for example, on each RP and on each line card where distributed Cisco Express Forwarding is active).

Each entry added to a FIB table or the adjacency table has a new field that records the current epoch for that table at the time the entry was added. When an entry is modified, the epoch of the entry is updated to record the table's current epoch. A record is kept of how many entries exist from each epoch. The epoch number cannot be incremented if any existing entries have the same epoch number as the next epoch value.

When the routing protocols signal that they have converged, all FIB and adjacency entries that have epoch numbers older than the current epoch number are removed from the FIB and adjacency tables.

When you need a Cisco Express Forwarding table to be rebuilt, the epoch number for that table is incremented, and the table is rebuilt in place. When rebuilding is complete, "stale" entries are removed from the table. You can increment the epoch of a single table or multiple tables at the same time when you enter the clear ip cef epoch [all-vrfs | full | vrf[table]] command. See the When to Refresh the CEF or Adjacency Tables section for information on when you might need to rebuild a Cisco Express Forwarding table.

When you display information from a Cisco Express Forwarding table (for example, with the show ip cef epochcommand), the table epoch is shown in the summary table. When detailed information is displayed for each table entry, the epoch number of each entry is shown.

Epoch Synchronization Between the RP and Line Cards

When FIB or adjacency entries are distributed from the central tables on the RP, the updates contain the epoch of the entry, ensuring that the distinction between old and new entries is maintained in distributed systems.

When a table is initialized on a line card, the current epoch of the table on the RP is sent to the line card. When the epoch is incremented on the RP, an event indicating that a new epoch has begun is sent to each line card.

Epoch Numbering for Routers That Support HA

In a router that supports high availability (HA), the epoch numbers for all Cisco Express Forwarding tables are incremented when an RP transitions from standby mode to active. After switchover, the active secondary RP initially has FIB and adjacency databases that are the same as those of the primary RP. When the epoch number for each table is incremented, all existing entries are considered stale. However, forwarding continues as normal. As the routing protocols start to repopulate the FIB and adjacency databases, existing and new entries receive the new epoch number, indicating that the entries have been refreshed.

When to Refresh the CEF or Adjacency Tables

You refresh or rebuild the Cisco Express Forwarding or adjacency tables when the tables contain inconsistencies.

Cisco 7500 series and Cisco 12000 Series Internet routers support distributed Cisco Express Forwarding, in which line cards make forwarding decisions based on stored copies of the same FIB and adjacency tables that are found on the RP. The tables on the line cards and the RP must remain synchronized.

Inconsistencies occur when forwarding information (a prefix) is missing on a line card, or the next-hop IP address on the line card is not the same as the next-hop IP address on the RP. Because updates to the RP and line card databases are not synchronous, fleeting inconsistencies can result.

Cisco Express Forwarding consistency checkers detect when forwarding information on the line cards and the RP lose synchronization. For more information on consistency checkers, see the Configuring Cisco Express Forwarding Consistency Checkers for Route Processors and Line Cards module.

How to Configure Epochs

This section contains instructions on how to configure epochs for Cisco Express Forwarding tables. Perform the following tasks to begin new epochs and increment the epoch number of the adjacency and Cisco Express Forwarding tables:

- Incrementing the Epoch Number of the Adjacency Table

- Incrementing the Epoch Number of One or All CEF Tables

- Verifying Epoch Information

Incrementing the Epoch Number of the Adjacency Table

Perform the following task to begin a new epoch and increment the epoch number of the adjacency table.

Use this task when you need to rebuild the adjacency table. A new adjacency table might be required because you need to remove inconsistencies from the table.

SUMMARY STEPS

1.    enable

2.    show ip cef epoch

3.    clear adjacency table

4.    show ip cef epoch

5.    exit

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

show ip cef epoch

Example:

Router# show ip cef epoch

Displays entries in the forwarding information base (FIB) or displays a summary of the FIB.

- The epoch keyword displays the table epochs of the adjacency table and all FIB tables.

Step 3

clear adjacency table

Example:

Router# clear adjacency table

Begins a new epoch and increments the epoch number of the adjacency table.

Step 4

show ip cef epoch

Example:

Router# show ip cef epoch

Displays entries in the FIB or displays a summary of the FIB.

- The epoch keyword displays the table epochs of the adjacency table and all FIB tables.

Step 5

exit

Example:

Router# exit

Exits to user EXEC mode.

Incrementing the Epoch Number of One or All CEF Tables

Perform the following task to begin a new epoch and increment the epoch number of one or all of the Cisco Express Forwarding tables.

Use the clear ip cef epoch command when you want to rebuild a Cisco Express Forwarding table. This command increments the epoch and flushes entries associated with the old epoch. This command also clears any inconsistencies that might exist between Cisco Express Forwarding tables on the RP and Cisco Express Forwarding tables on the line cards. If everything in the system is working correctly, the command has no effect on the Cisco Express Forwarding forwarding tables, other than changing the current epoch values.

SUMMARY STEPS

1.    enable

2.    show ip cef epoch

3.    clear ip cef epoch [all-vrfs | full | vrf [table]]

4.    show ip cef epoch

5.    exit

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

show ip cef epoch

Example:

Router# show ip cef epoch

Displays entries in the FIB or displays a summary of the FIB.

- The epoch keyword displays the table epochs of the adjacency table and all FIB tables.

Step 3

clear ip cef epoch [all-vrfs | full | vrf [table]]

Example:

Router# clear ip cef epoch full

Begins a new epoch and increments the epoch number of one or all Cisco Express Forwarding tables.

- The all-vrfs keyword begins a new epoch for all FIB tables.

- The full keyword begins a new epoch for all tables, including adjacency tables.

- The vrf keyword begins a new epoch for the specified FIB table.

- The table argument is the name of a specific Virtual Private Network (VPN) routing and forwarding instance (VRF).

Step 4

show ip cef epoch

Example:

Router# show ip cef epoch

Displays entries in the FIB or displays a summary of the FIB.

- The epoch keyword displays the epochs of the adjacency table and all FIB tables.

Step 5

exit

Example:

Router# exit

Exits to user EXEC mode.

Verifying Epoch Information

Perform the following task to verify epoch information for Cisco Express Forwarding and adjacency tables.

SUMMARY STEPS

1.    enable

2.    show adjacency summary detail

3.    show adjacency summary

4.    show ip cef epoch

5.    exit

DETAILED STEPS

Step 1

enable

Use this command to enable privileged EXEC mode. For example:

Example:

Router> enable

Enter your password if prompted.

Step 2

show adjacency summary detail

Use this command to verify that the epoch number is displayed for each entry in the adjacency table as you expect. For example:

Example:

Router# show adjacency detail
Protocol Interface                 Address
IP       Serial5/0/0/1:1           point2point(7)
0 packets, 0 bytes
0F000800
CEF   expires: 00:02:09
refresh: 00:00:09
Epoch: 14
IP       Serial5/0/1/1:1           point2point(7)
0 packets, 0 bytes
0F000800
CEF   expires: 00:02:09
refresh: 00:00:09
Epoch: 14

The epoch number is displayed for each entry in the adjacency table. In this example, the epoch number of each entry is 14.

Step 3

show adjacency summary

Use this command to verify that the epoch number for each adjacency in the adjacency table is as you expect. For example:

Example:

Router# show adjacency summary
Adjacency Table has 2 adjacencies
Table epoch: 14 (2 entries at this epoch)

Interface                 Adjacency Count
Serial5/0/0/1:1           1
Serial5/0/1/1:1           1

Use the epoch information in the summary section to verify that the epoch number for each adjacency in the adjacency table is as expected. The epoch number is 14 in this example, the same as the epoch number displayed in the show adjacency detail command in the previous step.

Step 4

show ip cef epoch

Use this command to verify that Cisco Express Forwarding information in all FIB tables, including the adjacency table, is as you expect.

In the following example, Cisco Express Forwarding epoch information is verified for all FIB tables, including the adjacency table:

Example:

Router# show ip cef epoch
CEF epoch information:

Table: Default-table
Table epoch: 77 (19 entries at this epoch)

Adjacency table
Table epoch: 16 (2 entries at this epoch)

Step 5

exit

Use this command to exit to user EXEC mode. For example:

Example:

Router# exit
Router>

Configuration Examples for Epochs

- Example Incrementing the Epoch Number of the Adjacency Table

- Example Incrementing the Epoch Number of One or All CEF Tables

Example Incrementing the Epoch Number of the Adjacency Table

The following example shows how to begin a new epoch and increment the epoch number of the adjacency table:

Router# show ip cef epoch
CEF epoch information:
Table: Default-table
Table epoch: 2 (43 entries at this epoch)
Adjacency table
Table epoch: 2 (5 entries at this epoch)
Router# clear adjacency table

After clearing:

Router# show ip cef epoch
CEF epoch information:
Table: Default-table
Table epoch: 3 (43 entries at this epoch)
Adjacency table
Table epoch: 3 (5 entries at this epoch)

Example Incrementing the Epoch Number of One or All CEF Tables

The following example shows how to begin a new epoch and increment the epoch number of all Cisco Express Forwarding tables:

Router# clear ip cef epoch full

The following example shows the output before and after you clear the epoch table and increment the epoch number. Before clearing:

router# show ip cef epoch
CEF epoch information:
Table: Default-table
Table epoch: 3 (43 entries at this epoch)
Adjacency table
Table epoch: 3 (5 entries at this epoch)

After clearing:

router# clear ip cef epoch full
router# show ip cef epoch
CEF epoch information:
Table: Default-table
Table epoch: 4 (43 entries at this epoch)
Adjacency table
Table epoch: 4 (5 entries at this epoch)

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

IP switching commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples.

Cisco IOS IP Switching Command Reference

Overview of the Cisco Express Forwarding feature

Cisco Express Forwarding Overview

Tasks for verifying basic Cisco Express Forwarding and distributed Cisco Express Forwarding operation

Configuring Basic Cisco Express Forwarding for Improved Performance, Scalability, and Resiliency in Dynamic Networks

Tasks for enabling or disabling Cisco Express Forwarding or distributed Cisco Express Forwarding

Enabling or Disabling Cisco Express Forwarding or Distributed Cisco Express Forwarding to Customize Switching and Forwarding for Dynamic Networks

Tasks for configuring a load-balancing scheme for Cisco Express Forwarding

Configuring a Load-Balancing Scheme for Cisco Express Forwarding Traffic

Tasks for configuring Cisco Express Forwarding consistency checkers

Configuring Cisco Express Forwarding Consistency Checkers for Route Processors and Line Cards

Tasks for configuring and verifying Cisco Express Forwarding network accounting

Configuring Cisco Express Forwarding Network Accounting

Tasks for customizing the display of recorded Cisco Express Forwarding events

Customizing the Display of Recorded Cisco Express Forwarding Events

Troubleshooting tips for incomplete adjacencies

Click Here Troubleshooting Incomplete Adjacencies with CEF

Description and use of the Cisco Express Forwarding consistency checkers available for the Cisco 7500 and 12000 series routers

Troubleshooting Prefix Inconsistencies with Cisco Express Forwarding

Explanation of and troubleshooting information for the Cisco IOS software implementation of Layer 3 load balancing across multiple parallel links when Cisco Express Forwarding is used

Troubleshooting Load Balancing Over Parallel Links Using Cisco Express Forwarding

Causes of common Cisco Express Forwarding-related error messages on platforms running distributed Cisco Express Forwarding switching (Cisco 7500 series routers and Cisco 12000 Series Internet routers) and how to troubleshoot them

Troubleshooting Cisco Express Forwarding-Related Error Messages

Standard

Standards

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

--

MIB

MIBs

MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

Click Here

RFC

RFCs

Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

--

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

Click Here

Feature Information for Configuring Epochs

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.

Feature Information for Configuring Epochs to Clear and Rebuild Cisco Express Forwarding and Adjacency Tables

Feature Name

Releases

Feature Configuration Information

Nonstop Forwarding Enhanced FIB Refresh

12.2(8)T

This feature allows you to clear the forwarding table on demand and to continue forwarding through the use of the old entries in the table while the new forwarding table is being built.

Glossary

adjacency --A relationship formed between selected neighboring routers and end nodes for the purpose of exchanging routing information. Adjacency is based upon the use of a common media segment by the routers and nodes involved.

Cisco Express Forwarding --A Layer 3 switching technology. Cisco Express Forwarding can also refer to central Cisco Express Forwarding mode, one of two modes of Cisco Express Forwarding operation. Cisco Express Forwarding enables a Route Processor to perform express forwarding. Distributed Cisco Express Forwarding is the other mode of Cisco Express Forwarding operation.

distributed Cisco Express Forwarding --A mode of Cisco Express Forwarding operation in which line cards (such as Versatile Interface Processor (VIP) line cards) maintain identical copies of the forwarding information base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters; this relieves the Route Switch Processor of involvement in the switching operation.

FIB --forwarding information base. A component of Cisco Express Forwarding that is conceptually similar to a routing table or information base. The router uses the FIB lookup table to make destination-based switching decisions during Cisco Express Forwarding operation. The router maintains a mirror image of the forwarding information in an IP routing table.

LIB --label information base. A database used by a label switch router (LSR) to store labels learned from other LSRs, as well as labels assigned by the local LSR.

line card --A general term for an interface processor that can be used in various Cisco products. For example, a Versatile Interface Processor (VIP) is a line card for the Cisco 7500 series router.

prefix --The network address portion of an IP address. A prefix is specified by a network and mask and is generally represented in the format network/mask. The mask indicates which bits are the network bits. For example, 1.0.0.0/16 means that the first 16 bits of the IP address are masked, making them the network bits. The remaining bits are the host bits. In this example, the network number is 10.0.

RIB --Routing Information Base. A central repository of routes that contains Layer 3 reachability information and destination IP addresses or prefixes. The RIB is also known as the routing table.

RP --Route Processor. The processor module in the Cisco 7000 series routers that contains the CPU, system software, and most of the memory components that are used in the router. It is sometimes called a supervisory processor.

RSP --Route Switch Processor. The processor module used in the Cisco 7500 series routers that integrates the functions of the Route Processor (RP) and the Switch Processor (SP).

SP --Switch Processor. Cisco 7000-series processor module that acts as the administrator for all CxBus activities. Sometimes called CiscoBus controller.

Chapter 6. Configuring CEF Consistency Checkers

This module contains information about and instructions for configuring Cisco Express Forwarding consistency checkers for route processors and line cards. Cisco Express Forwarding consistency checkers help you find any database inconsistencies, such as an IP prefix missing from a line card or a Route Processor (RP). You can investigate and resolve the inconsistency by examining the associated Cisco Express Forwarding system error messages that occur and by issuing Cisco Express Forwarding debug and show commands.

Cisco Express Forwarding is an advanced Layer 3 IP switching technology. It optimizes network performance and scalability for all kinds of networks: those that carry small amounts of traffic and those that carry large amounts of traffic in complex patterns, such as the Internet and networks characterized by intensive web-based applications or interactive sessions.

- Finding Feature Information

- Prerequisites for CEF Consistency Checkers

- Restrictions for CEF Consistency Checkers

- Information About CEF Consistency Checkers

- How to Configure CEF Consistency Checkers

- Configuration Examples for CEF Consistency Checkers

- Additional References

- Feature Information for CEF Consistency Checkers

- Glossary

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to Click Here . An account on Cisco.com is not required.

Prerequisites for CEF Consistency Checkers

Cisco Express Forwarding must be up and running on the networking device before you can configure Cisco Express Forwarding consistency checkers.

Restrictions for CEF Consistency Checkers

The Cisco Express Forwarding consistency checkers lc-detect and scan-lc apply only to devices that have distributed Cisco Express Forwarding enabled.

Information About CEF Consistency Checkers

- Cisco Platform Support for CEF and dCEF

- CEF Consistency Checker Types

Cisco Platform Support for CEF and dCEF

Cisco Express Forwarding is enabled by default on most Cisco platforms running Cisco IOS software Release12.0 or later. When Cisco Express Forwarding is enabled on a router, the RP performs the express forwarding.

To find out if Cisco Express Forwarding is enabled on your platform, enter the show ip cefcommand. If Cisco Express Forwarding is enabled, you receive output that looks like this:

Router# show ip cef
Prefix              Next Hop            Interface
[...]
10.2.61.8/24        192.168.100.1       FastEthernet1/0/0
192.168.101.1       FastEthernet6/1
[...]

If Cisco Express Forwarding is not enabled on your platform, the output for the show ip cefcommand looks like this:

Router# show ip cef
%CEF not running

Distributed Cisco Express Forwarding is enabled by default on the Catalyst 6500 series switch, the Cisco 7500 series router, and the Cisco 12000 Series Internet Router. When distributed Cisco Express Forwarding is enabled on your platform, the line cards perform the express forwarding.

If Cisco Express Forwarding is not enabled on your platform, use the ip cefcommand to enable Cisco Express Forwarding or the ip cef distributed command to enable distributed Cisco Express Forwarding.

CEF Consistency Checker Types

Cisco Express Forwarding uses routing information that is retrieved from the Routing Information Base (RIB), the RP, and the line card databases to perform express forwarding. As these databases are updated, inconsistencies might result, due to the asynchronous nature of the distribution mechanism for these databases. Inconsistencies caused by asynchronous database distribution are of the following types:

- Missing information, such as a particular prefix, on a line card

- Different information, such as different next hop IP addresses, on the line card

Cisco Express Forwarding supports passive and active consistency checkers that run independently to uncover these forwarding inconsistencies. The table below describes the consistency checkers and indicates whether the checker operates on the RP or the line card.

Types of Cisco Express Forwarding Consistency Checkers

Checker Type

Operates On

Description

Lc-detect

Line card

(Distributed Cisco Express Forwarding only) Retrieves IP prefixes found missing from the line card FIB table. If IP prefixes are missing, the line card cannot forward packets for the corresponding addresses. Lc-detect then sends IP prefixes to the RP for confirmation. If the RP finds that it has the relevant entry, an inconsistency is detected, and an error message is displayed. Also, the RP sends a signal back to the line card confirming that the IP prefix contributes to the creation of an inconsistency.

Scan-lc

Line card

(Distributed Cisco Express Forwarding only) Looks through the FIB table for a configurable time period and sends the next n prefixes to the RP. The RP does an exact lookup in its FIB table. If the RP finds that the prefix is missing, the RP reports an inconsistency. The RP sends a signal back to the line card for confirmation.

The time period and number of prefixes sent are configured with the ip cef table consistency-check command.

Scan-rp

Route Processor

Looks through the RP FIB table for a configurable time period and sends the next n prefixes to the line card. (This action is opposite to the one that the scan-lc checker performs.) The line card does an exact lookup in the FIB table. If the line card finds the prefix missing, the line card reports an inconsistency and signals the RP for confirmation.

The time period and number of prefixes sent are configured with the ip cef table consistency-check command.

Scan-rib

Route Processor

Operates on all (even nondistributed) RPs, and scans the RIB to ensure that prefix entries are present in the RP FIB table.

Cisco Express Forwarding consistency checkers are enabled by default for Cisco IOS Releases 12.0(20)S and later. Console errors are disabled by default.

If you find a database inconsistency, such as an IP prefix missing from a line card or an RP, you can investigate and resolve it by examining the Cisco Express Forwarding system error messages and by issuing Cisco Express Forwarding debug and show commands.

For Cisco Express Forwarding consistency checker system error messages, see the System Message Guide for your Cisco IOS Release.

How to Configure CEF Consistency Checkers

- Enabling CEF Consistency Checkers

- Displaying and Clearing Table Inconsistencies

Enabling CEF Consistency Checkers

Perform the following task to enable Cisco Express Forwarding consistency checkers.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ip cef table consistency-check [type {lc-detect | scan-lc | scan-rib | scan-rp }] [count count-number ] [period seconds ]

4.    ip cef table consistency-check [settle-time seconds]

5.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

ip cef table consistency-check [type {lc-detect | scan-lc | scan-rib | scan-rp }] [count count-number ] [period seconds ]

Example:

Router(config)# ip cef table consistency-check scan-rib count 100
period 60

Enables Cisco Express Forwarding table consistency checker types and parameters.

- The type keyword indicates the type of consistency check to enable.

- The lc-detect keyword enables the line card to detect a missing prefix, which is confirmed by the RP.

- The scan-lckeyword enables a passive scan check of tables on the line card.

- The scan-rib keyword enables a passive scan check of tables on the RP and a comparison with the RIB.

- The scan-rp keyword enables a passive scan check of tables on the RP.

- The count -number keyword-argument pair is the maximum number of prefixes to check per scan. The range is from 1 to 225.

- The period seconds keyword-argument pair is the time during which updates for a candidate prefix are ignored as inconsistencies. The range is from 1 to 3600 seconds.

Step 4

ip cef table consistency-check [settle-time seconds]

Example:

Router(config)# ip cef table consistency-check settle-time 65

Suppresses inconsistency errors during route updates.

- The settle-time seconds keyword-argument pair is the time elapsed during which updates for a candidate prefix are ignored as inconsistencies. The range is from 1 to 3600 seconds.

Step 5

end

Example:

Router(config)# end

Exits to privileged EXEC mode.

Displaying and Clearing Table Inconsistencies

Perform the following task to display and clear Cisco Express Forwarding table inconsistency records found by the lc-detect, scan-rp, scan-rib, and scan-lc detection mechanisms.

SUMMARY STEPS

1.    enable

2.    show ip cef inconsistency

3.    clear ip cef inconsistency

4.    clear cef linecard [slot-number] [adjacency | interface | prefix]

5.    show ip cef inconsistency

6.    exit

DETAILED STEPS

Step 1

enable

Use this command to enable privileged EXEC mode. For example:

Example:

Router> enable

Enter your password if prompted.

Step 2

show ip cef inconsistency

Use this command to display Cisco Express Forwarding IP inconsistencies. For example:

Example:

Router# show ip cef inconsistency
Table consistency checkers (settle time 65s)
lc-detect:running
0/0/0 queries sent/ignored/received
scan-lc:running [100 prefixes checked every 60s]
0/0/0 queries sent/ignored/received
scan-rp:running [100 prefixes checked every 60s]
0/0/0 queries sent/ignored/received
scan-rib:running [100 prefixes checked every 60s]
0/0/0 queries sent/ignored/received
Inconsistencies:0 confirmed, 0/16 recorded

For each checker type, the output shows the number of prefixes that Cisco Express Forwarding must check and the number of seconds (the settle time) during which an inconsistency between RP and line card tables is ignored. The preceding output shows that 0 inconsistencies existed between these tables at the time the command was entered on the router.

Step 3

clear ip cef inconsistency

Use this command to clear the Cisco Express Forwarding inconsistency statistics and records found by the Cisco Express Forwarding consistency checkers. For example:

Example:

Router# clear ip cef inconsistency

Step 4

clear cef linecard [slot-number] [adjacency | interface | prefix]

Use this command to clear Cisco Express Forwarding information from line cards. For example:

Router# clear cef linecard

Example:

Step 5

show ip cef inconsistency

Use this command to verify that Cisco Express Forwarding statistics on inconsistencies are removed from the RP and the line cards. For example:

Example:

Router# show ip cef inconsistency
Table consistency checkers (settle time 65s)
lc-detect:running
0/0/0 queries sent/ignored/received
scan-lc:running [100 prefixes checked every 60s]
0/0/0 queries sent/ignored/received
scan-rp:running [100 prefixes checked every 60s]
0/0/0 queries sent/ignored/received
scan-rib:running [1000 prefixes checked every 60s]
0/0/0 queries sent/ignored/received
Inconsistencies:0 confirmed, 0/16 recorded

This sample output shows that four consistency checkers are enabled, that each checker sends 100 prefixes to be checked every 60 seconds, and that the time during which inconsistencies are ignored is 65 seconds. In this example, no inconsistencies were found.

Example:

Step 6

exit

Use this command to exit to user EXEC mode. For example:

Example:

Router# exit
Router>

Configuration Examples for CEF Consistency Checkers

- Example Enabling CEF Consistency Checkers

Example Enabling CEF Consistency Checkers

The following example shows how to enable the scan-rp Cisco Express Forwarding consistency checker.

configure terminal
!
ip cef table consistency-check scan-rp count 225 period 3600
ip cef table consistency-check settle-time 2500
end

The RP is configured to send 3600 prefixes to the line cards every 225 seconds. After the prefixes are sent, the line cards are to wait 2500 seconds before signaling the RP to report an inconsistency (if there is one).

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

IP switching commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples.

Cisco IOS IP Switching Command Reference

Troubleshooting tips for incomplete adjacencies

Troubleshooting Incomplete Adjacencies with CEF

Description of and troubleshooting information for the consistency checker available for the Cisco 7500 series and Cisco 12000 Series Internet routers

Troubleshooting Prefix Inconsistencies with Cisco Express Forwarding

Overview of the Cisco Express Forwarding feature

Cisco Express Forwarding Overview

Tasks for verifying basic Cisco Express Forwarding and distributed Cisco Express Forwarding operation

Configuring Basic Cisco Express Forwarding for Improved Performance, Scalability, and Resiliency in Dynamic Networks

Tasks for enabling or disabling Cisco Express Forwarding or distributed Cisco Express Forwarding

Enabling or Disabling Cisco Express Forwarding or Distributed Cisco Express Forwarding to Customize Switching and Forwarding for Dynamic Networks"

Tasks for configuring a load-balancing scheme for Cisco Express Forwarding

Configuring a Load-Balancing Scheme for Cisco Express Forwarding Traffic

Tasks for configuring epochs for Cisco Express Forwarding tables

Configuring Epochs to Clear and Rebuild Cisco Express Forwarding and Adjacency Tables

Tasks for configuring and verifying Cisco Express Forwarding network accounting

Configuring Cisco Express Forwarding Network Accounting

Tasks for customizing the display of recorded Cisco Express Forwarding events

Customizing the Display of Recorded Cisco Express Forwarding Events

Causes of common Cisco Express Forwarding-related error messages on platforms running distributed Cisco Express Forwarding switching (Cisco 7500 series routers and Cisco 12000 Series Internet routers) and how to troubleshoot them

Troubleshooting Cisco Express Forwarding-Related Error Messages

Standards

Standard

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

--

MIBs

MIB

MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

Click Here

RFCs

RFC

Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

--

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

Click Here

Feature Information for CEF Consistency Checkers

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.

Feature Information for Configuring Basic Cisco Express Forwarding Consistency Checkers for Route Processors and Line Cards

Feature Name

Releases

Feature Configuration Information

This table is intentionally left blank because no features were introduced or modified in Cisco IOS Release 12.2(1) or later. This table will be updated when feature information is added to this module.

--

--

Glossary

adjacency --A relationship formed between selected neighboring routers and end nodes for the purpose of exchanging routing information. Adjacency is based upon the use of a common media segment by the routers and nodes involved.

Cisco Express Forwarding --A Layer 3 switching technology. Cisco Express Forwarding can also refer to central Cisco Express Forwarding mode, one of two modes of Cisco Express Forwarding operation. Cisco Express Forwarding enables a Route Processor to perform express forwarding. Distributed Cisco Express Forwarding is the other mode of Cisco Express Forwarding operation.

distributed Cisco Express Forwarding --A mode of Cisco Express Forwarding switching in which line cards (such as Versatile Interface Processor (VIP) line cards) maintain identical copies of the forwarding information base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters; this relieves the Route Switch Processor of involvement in the switching operation.

FIB --forwarding information base. A component of Cisco Express Forwarding that is conceptually similar to a routing table or information base. The router uses the FIB lookup table to make destination-based switching decisions during Cisco Express Forwarding operation. The router maintains a mirror image of the forwarding information in an IP routing table.

IPC --interprocess communication. The mechanism that enables the distribution of Cisco Express Forwarding tables from the Route Switch Processor (RSP) to the line card when the router is operating in distributed Cisco Express Forwarding mode.

LIB --label information base. A database used by a label switch router (LSR) to store labels learned from other LSRs, as well as labels assigned by the local LSR.

line card --A general term for an interface processor that can be used in various Cisco products. For example, a Versatile Interface Processor (VIP) is a line card for the Cisco 7500 series router.

MPLS --Multiprotocol Label Switching. An emerging industry standard for the forwarding of packets along the normal routing paths (sometimes called MPLS hop-by-hop forwarding).

prefix --The network address portion of an IP address. A prefix is specified by a network and mask and is generally represented in the format network/mask. The mask indicates which bits are the network bits. For example, 1.0.0.0/16 means that the first 16 bits of the IP address are masked, making them the network bits. The remaining bits are the host bits. In this example, the network number is 10.0.

RIB --Routing Information Base. A central repository of routes that contains Layer 3 reachability information and destination IP addresses or prefixes. The RIB is also known as the routing table.

RP --Route Processor. The processor module in the Cisco 7000 series routers that contains the CPU, system software, and most of the memory components that are used in the router. It is sometimes called a supervisory processor.

VPN --Virtual Private Network. The result of a router configuration that enables IP traffic to use tunneling to travel securely over a public TCP/IP network.

VRF --A Virtual Private Network (VPN) routing/forwarding instance. A VRF consists of an IP routing table, a derived forwarding table, a set of interfaces that use the forwarding table, and a set of rules and routing protocols that determine what goes into the forwarding table. In general, a VRF includes the routing information that defines a customer VPN site that is attached to a PE router.

Chapter 7. Configuring CEF Network Accounting

This module contains information about and instructions for configuring network accounting for Cisco Express Forwarding. Accounting produces the statistics that enable you to better understand Cisco Express Forwarding patterns in your network. For example, you might want to find out the number of packets and bytes switched to a destination or the number of packets switched through a destination.

Cisco Express Forwarding is an advanced Layer 3 IP switching technology. It optimizes network performance and scalability for all kinds of networks: those that carry small amounts of traffic and those that carry large amounts of traffic in complex patterns, such as the Internet and networks characterized by intensive web-based applications or interactive sessions.

- Finding Feature Information

- Prerequisites for CEF Network Accounting

- Restrictions for CEF Network Accounting

- Information About CEF Network Accounting

- How to Configure CEF Network Accounting

- Configuration Examples for CEF Network Accounting

- Additional References

- Feature Information for CEF Network Accounting

- Glossary

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to Click Here . An account on Cisco.com is not required.

Prerequisites for CEF Network Accounting

Cisco Express Forwarding must be up and running on the networking device before you can configure network accounting for Cisco Express Forwarding. See the Cisco Platform Support for Central CEF and dCEF section for information on how to determine if Cisco Express Forwarding is enabled on your networking device.

Restrictions for CEF Network Accounting

- The ip cef accounting command is not supported on Cisco 7600 Series Routers.

Information About CEF Network Accounting

For links to information about other Cisco Express Forwarding and distributed Cisco Express Forwarding features that you can configure, go to the Additional References.

- Cisco Platform Support for Central CEF and dCEF

- Traffic Matrix Statistics

- TMS and CEF Nonrecursive Accounting

- How Backbone Routers Collect TMS

- TMS Viewing Options

- Statistics in the timestats File

- Statistics in the tmsasinfo File

Cisco Platform Support for Central CEF and dCEF

Cisco Express Forwarding is enabled by default on most Cisco platforms running Cisco IOS software Release 12.0 or later. When Cisco Express Forwarding is enabled on a router, the Route Processor (RP) performs the express forwarding.

To find out if Cisco Express Forwarding is enabled on your platform, enter the show ip cef command. If Cisco Express Forwarding is enabled, you will receive the following output:

Device# show ip cef
Prefix              Next Hop            Interface
[...]
10.2.61.8/24        192.168.100.1       FastEthernet1/0/0
192.168.101.1       FastEthernet6/1
[...]

If Cisco Express Forwarding is not enabled on your platform, the following output for the show ip cef command is displayed:

Device# show ip cef
%CEF not running

Distributed Cisco Express Forwarding is enabled by default on the Catalyst 6500 series switch, the Cisco 7500 series router, and the Cisco 12000 Series Internet Router. When distributed Cisco Express Forwarding is enabled on your platform, the line cards perform the express forwarding.

If Cisco Express Forwarding is not enabled on your platform, use the ip cef command to enable (central) Cisco Express Forwarding or the ip cef distributed command to enable distributed Cisco Express Forwarding.

Central Cisco Express Forwarding or distributed Cisco Express Forwarding has the following restrictions:

- The Cisco 12000 Series Internet routers operate only in distributed Cisco Express Forwarding mode. On these routers, you must not disable distributed Cisco Express Forwarding on an interface.

- If you enable Cisco Express Forwarding and then create an access list that uses the logkeyword, the packets that match the access list are not Cisco Express Forwarding switched. They are process switched. Logging disables Cisco Express Forwarding.

- Distributed Cisco Express Forwarding switching cannot be configured on the same VIP card on which distributed fast switching is configured.

- Distributed Cisco Express Forwarding is not supported on Cisco 7200 series routers.

See the Additional References for links to more information on the features and functionality of Cisco Express Forwarding.

Traffic Matrix Statistics

The traffic matrix statistics (TMS) feature allows an administrator to gather the following data:

- The number of packets and number of bytes that travel across the backbone from internal and external sources. The counts of packets and bytes are called TMS and are useful for determining how much traffic a backbone handles. You can analyze TMS using the following methods:

- Collecting and viewing TMS through the application of the Network Data Analyzer (NDA)

- Reading the TMS that reside on the backbone router

- The neighbor autonomous systems of a Border Gateway Protocol (BGP) destination. You can view these systems by reading the tmasinfo_ascii file on the backbone router.

The following sections explain how to collect and view the TMS using the command-line interface (CLI) and the NDA. For detailed instructions on using the NDA, see the Network Data Analyzer Installation and User Guide .

TMS and CEF Nonrecursive Accounting

TMS enables an administrator to capture and analyze data on traffic entering a backbone that is running BGP. The TMS feature also allows an administrator to determine the neighbor autonomous systems of a BGP destination. TMS are counted during packet forwarding by Cisco Express Forwarding nonrecursive accounting.

By enabling a backbone router to gather TMS, you can determine the amount of traffic that enters the backbone from sites outside of the backbone. You can also determine the amount of traffic that is generated within the backbone. This information helps you optimize and manage traffic across the backbone.

The following paragraphs explain how Cisco Express Forwarding nonrecursive accounting aggregates packet statistics for Interior Gateway Protocol (IGP) routes and their dependent BGP routes.

A BGP network deployed by a service provider might have the following components:

- IGP routes that describe the next hop to which traffic should be sent

- BGP routes that specify an intermediate address to which traffic should be sent

The intermediate address specified for the BGP route might be several hops away from the provider edge (PE) router. The next hop for the BGP route is the next hop for the intermediate address of the BGP route. The BGP route is called recursive, because it points through an intermediate address to an IGP route that provides the next hop for forwarding. However, a route lookup results in a next hop that is not directly reachable, as is the case with the BGP route’s intermediate address. A recursive lookup to an IGP route is used to decide how to reach the indirect next hop.

Cisco Express Forwarding represents IGP routes as nonrecursive entries and BGP routes as recursive entries that resolve through nonrecursive entries.

Cisco Express Forwarding nonrecursive accounting counts the packets for all of the Cisco Express Forwarding recursive entries (from BGP routes) that resolve through a Cisco Express Forwarding nonrecursive entry and the packets for the nonrecursive entry (from IGP routes). The number of packets is totalled in one location.

The packets forwarded based on a nonrecursive Cisco Express Forwarding entry can be split into two bins based on whether the input interface of the backbone router is configured as internal or external. Thus, all packets that arrive on external interfaces (external to the region of interest) and are forwarded based on a given IGP route (either directly or through a recursive BGP route) are counted together.

The following example shows how Cisco Express Forwarding nonrecursive accounting counts packets when BGP routes resolve to one IGP route and when they do not.

A multiaccess network access point (NAP) has BGP routes referring to hosts on the NAP network.

- If the network is advertised as a single IGP route, all of the BGP routes to the various hosts at that NAP resolve to a single IGP route. Cisco Express Forwarding nonrecursive accounting counts the number of packets sent to all BGP destinations.

- If a network administrator instead advertises individual host routes from the NAP network to the IGP, Cisco Express Forwarding nonrecursive accounting counts packets to those hosts separately.

How Backbone Routers Collect TMS

You can determine the amount of traffic that enters the backbone from sites outside of the backbone if you enable a backbone router to gather TMS. You can also determine the amount of traffic that is generated within the backbone. This information helps you optimize and manage traffic across the backbone. The two figures below help illustrate the traffic statistics you can gather using TMS.

The figure below shows a sample network with backbone routers and links. The traffic that travels through the backbone is the area of interest for TMS collection. TMS are collected during packet forwarding. The backbone is represented by the darkly shaded routers and bold links. The lighter shaded and unshaded routers are outside the backbone.

Sample Network with Backbone Routers and Links

The figure below shows an exploded view of the backbone router that links the Los Angeles point of presence (POP) in the figure above to the Atlanta POP. The bold line represents the backbone link going to the Atlanta POP.

The figure below shows the following types of traffic that travel through the backbone router:

- The dotted line marked A represents traffic entering the backbone from a router that is not part of the backbone. This is called external traffic.

- The dotted lines marked B and D represent traffic that is exiting the backbone. This is called internal traffic.

- The dotted line marked C represents traffic that is not using the backbone and is not of interest to TMS.

Types of Traffic That Travel Through a Backbone Router

You can determine the amount of traffic the backbone handles by enabling a backbone router to track the number of packets and bytes that travel through the backbone router. You can separate the traffic into the categories "internal" and "external." You separate the traffic by designating incoming interfaces on the backbone router as internal or external.

Once you enable a backbone router to collect TMS, the router starts counters, which dynamically update when network traffic passes through the backbone router. You can retrieve a snapshot of the TMS, either through a command to the backbone router or through the NDA.

External traffic (path A in the figure above) is the most important for determining the amount of traffic that travels through a backbone router. Internal traffic (paths B and D in the figure above) is useful for ensuring that you are capturing all of the TMS data. When you receive a snapshot of the TMS, the packets and bytes are displayed in internal and external categories.

TMS Viewing Options

Once TMS are collected, you have three options for viewing the data:

- TMS Displayed with the NDA Display Module

- Nonrecursive Accounting Information Displayed

TMS Displayed with the NDA Display Module

The NDA collects TMS from the backbone router and displays the data through the NDA Display module. The TMS can look similar to the data shown in the two figures below. The display format depends on the aggregation scheme you select. See the Network Data Analyzer Installation and User Guide for more information.

(The view of data that the NDA Display module provides is wide. Slide the scroll bar to the right and left to see all of the data. The two figures below taken together show all of the columns of data.)

Displaying TMS Through the NDA (Part 1)

Displaying TMS Through the NDA (Part 2)

Nonrecursive Accounting Information Displayed

You can use the show ip cef command to display nonrecursive accounting information, including the counts of internal and external packets and bytes that have traveled through the IP prefix address/mask (in the format a.b.c.d/len) for an IGP route. Here is an example that shows 0 packets and 0 bytes of external traffic and 1144 packets and 742 bytes of internal traffic for the router with the IP address 10.102.102.102:

router# show ip cef 10.102.102.102
10.102.102.10/32, version 34, epoch 0, per-destination sharing
0 packets, 0 bytes
tag information set
local tag: 19
via 10.1.1.100, Ethernet0/0, 0 dependencies
next hop 10.1.1.100, Ethernet0/0
valid adjacency
tag rewrite with Et0/0, 10.1.1.100, tags imposed {17}
0 packets, 0 bytes switched through the prefix
tmstats: external 0 packets, 0 bytes
internal 1144 packets, 742 bytes
30 second output rate 0 Kbits/sec

Statistics in the timestats File

Before you perform the task to interpret the statistics in the tmstats_ascii file (an optional procedure described in the Interpreting the tmstats File section), you need to understand the following:

Virtual Files on the Backbone Router

You can read TMS that reside on the backbone router and are stored in the following virtual files:

- tmstats_ascii--TMS in ASCII (human readable) format

- tmstats_binary--TMS in binary (space-efficient) format

The binary file tmstats_binary contains the same information as the ASCII file, except in a space-efficient format. You can copy this file from the router and read it with any utility that accepts files in binary format.

tmstats File Header Description

The tmstats_ascii file header provides the address of the backbone router and information about how much time the router used to collect and export the TMS data. The header occupies one line and uses the following format:

VERSION 1|ADDR
<address>
|AGGREGATION
TrafficMatrix.ascii|SYSUPTIME
<seconds>|
routerUTC
<routerUTC>
|NTP
<synchronized|unsynchronized>|DURATION
<aggregateTime>
|

The table below describes the fields in the file header of the tmstats_ascii file.

Fields in tmstats_ascii File Header

Maximum Field Length

Field

Description

10

VERSION

File format version

21

ADDR

The IP address of the router

32

AGGREGATION

The type of data being aggregated

21

SYSUPTIME

The time of export (in seconds) since the router booted

21

routerUTC

The time of export (in seconds) since 1900-01-01 (Coordinated Universal Time (UTC)), as determined by the router

19

NTP

An indication of whether or not the UTC of the router has been synchronized by the Network Time Protocol (NTP) with an authoritative time source, such as a radio clock or an atomic clock attached to a time server

20

DURATION

The time needed to capture the data (in seconds) (trailing |)

Destination Prefix Record Description

The destination prefix record displays the internal and external packets and bytes for the IGP route and uses the following format:

p|
<destPrefix/Mask>
|
<creationSysUpTime>
|
<internalPackets>
|
<internalBytes>
|
<externalPackets>
|
<externalBytes>

The per-prefix records display information only about label switched traffic data. Label forwarding across a backbone router or switch, is based on either dynamic label switching or traffic engineered paths.

The table below describes the fields in the destination prefix record.

Destination Prefix Record Fields

Maximum Field Length

Field

Description

2

<recordType>

p means that the record represents dynamic label switching (for example, LDP) data or headend traffic engineering (TE) tunnel traffic data.

t means that the record contains TE tunnel midpoint data.

19

destPrefix/Mask

The IP prefix address/mask (in the format a.b.c.d/len) for this IGP route.

11

creationSysUpTime

How long the system had been running when the record was first created.

21

internalPackets

Internal packet count.

21

internalBytes

Internal byte count.

21

externalPackets

External packet count.

20

externalBytes

External byte count (no trailing |).

Tunnel Midpoint Record Description

The tunnel midpoint record displays the internal and external packets and bytes for the tunnel head and uses the following format:

t|
<headAddr><tun_id>
|
<creationSysUpTime>
|

<internalPackets>
|
<internalBytes>
|
<externalPackets>
|
<externalBytes>

The table below describes the fields in the tunnel midpoint record.

Tunnel Midpoint Record Fields

Maximum Field Length

Field

Description

2

<recordType>

t means that the record contains TE tunnel midpoint data.

27

headAddr<space>tun_id

The IP address of the tunnel head and tunnel interface number.

11

creationSysUpTime

How long the system had been running when the record was first created.

21

internalPackets

Internal packet count.

21

internalBytes

Internal byte count.

21

externalPackets

External packet count.

20

externalBytes

External byte count (no trailing |).

Statistics in the tmsasinfo File

Before viewing the statistics in thetmsasinfo file (an optional procedure described in the Viewing Information in the tmsasinfo File), you need to understand the following:

Header Format for tmsasinfo File

The file header provides the address of the router and indicates how much time the router used to collect and export the data. The file header uses the following format:

VERSION 1|ADDR
<address>
|AGGREGATION
ASList.ascii|SYSUPTIME
<seconds>|routerUTC

<routerUTC>
|DURATION
<aggregateTime>
|

The table below describes the fields in the file header.

Fields in the tmsasinfo File Header

Maximum Field Length

Field

Description

5

VERSION

File format version

15

ADDR

The IP address of the router

20

AGGREGATION

The type of data being aggregated

10

SYSUPTIME

The time of export (in seconds) since router booted

10

routerUTC

The time of export (in seconds) since 1900-01-01, as determined by the router

10

DURATION

The time needed to capture the data (in seconds)

Neighbor AS Record in the tmsasinfo File

The neighbor AS record displays the neighbor AS and the underlying prefix/mask for each BGP route. The record uses the following format:

<nonrecursivePrefix/Mask>
|
<AS>
|
<destinationPrefix/Mask>

The table below describes the fields in the neighbor AS record.

Neighbor AS Record Fields

Maximum Field Length

Field

Description

18

nonrecursivePrefix/Mask

The IP prefix address/mask (a.b.c.d/len format) for this IGP route

5

AS

The neighbor AS

18

destinationPrefix/Mask

The prefix/mask for the Forwarding Information Base (FIB) entry (typically BGP route)

How to Configure CEF Network Accounting

- Configuring CEF Network Accounting

- Enabling a Backbone Router to Collect TMS

- Interpreting the tmstats File

- Viewing Information in the tmsasinfo File

- Verifying CEF Network Accounting Information

Configuring CEF Network Accounting

Perform the following task to enable network accounting for Cisco Express Forwarding.

When you enable network accounting for Cisco Express Forwarding from the global configuration mode, accounting information is collected on the RP.

When you enable network accounting for distributed Cisco Express Forwarding from the global configuration mode, accounting information grouped by IP prefix (recursive or nonrecursive) is not sent to the RP, but is collected on the line card.

After accounting information is collected for Cisco Express Forwarding or distributed Cisco Express Forwarding, you can display the statistics using the show ip cef command. To verify the statistics on a line card, use the show cef interface statisticscommand.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ip cef accounting {[non-recursive] [per-prefix] [prefix-length]}

4.    exit

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

ip cef accounting {[non-recursive] [per-prefix] [prefix-length]}

Example:

Router(config)# ip cef accounting per-prefix

Enables Cisco Express Forwarding network accounting.

- The non-recursive keyword enables you to count the number of packets and bytes express forwarded through nonrecursive prefixes.

This keyword is optional when the command is used in global configuration mode.

- The per-prefix keyword enables you to count the number of packets and bytes express forwarded to a destination IP address (or prefix).

- The prefix-length keyword enables accounting based on prefix length.

Step 4

exit

Example:

Router(config)# exit

Exits to privileged EXEC mode.

Enabling a Backbone Router to Collect TMS

This section contains information about and instructions for enabling a backbone router to collect TMS for Cisco Express Forwarding. Enabling a backbone router to collect TMS requires enabling nonrecursive accounting and setting the interfaces on the router to collect internal or external TMS. The internal and external settings are used only for TMS collection. The interfaces are set to internal by default.

Note

Make sure you configure the collection of internal and external TMS on the incoming interface of the backbone router.

You can perform these tasks either through the CLI or through the NDA. The following sections explain each procedure:

- Using the CLI to Enable a Backbone Router to Collect TMS

- Enabling the NDA to Collect TMS on a Backbone Router

Using the CLI to Enable a Backbone Router to Collect TMS

Perform the following task to use the CLI to enable a backbone router to collect TMS.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ip cef

4.    ip cef accounting {[non-recursive [per-prefix] [prefix-length]}

5.    Do one of the following:

- interface type slot/port

- interface type slot/port-adapter/port

6.    ip cef accounting non-recursive {external | internal}

7.    exit

8.    Repeat Steps 5, 6, and 7 for each incoming interface that you want to configure for TMS.

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

ip cef

Example:

Router(config)# ip cef

Enables Cisco Express Forwarding on the route processor card.

Step 4

ip cef accounting {[non-recursive [per-prefix] [prefix-length]}

Example:

Router(config)# ip cef accounting non-recursive

Enables Cisco Express Forwarding network accounting.

- The non-recursive keyword enables you to count the number of packets and bytes express forwarded through nonrecursive prefixes.

This keyword is optional when the command is used in global configuration mode.

- The per-prefix keyword enables you to count the number of packets and bytes express forwarded to a destination (or prefix).

- The prefix-lengthkeyword enables accounting based on prefix length.

Step 5

Do one of the following:

- interface type slot/port

- interface type slot/port-adapter/port

Example:

Router(config)# interface ethernet 1/1

Example:

Example:

or

Example:

Router(config)# interface fastethernet 1/0/0

Configures an interface type and enters interface configuration mode.

- The type argument specifies the type of interface to be configured.

- The slot/ argument specifies the slot number. See the appropriate hardware manual for slot and port information.

- The port argument specifies the port number. See the appropriate hardware manual for slot and port information.

- The port-adapter/ argument specifies the port adapter number. See the appropriate hardware manual for information about port adapter compatibility.

This command specifies the interface on the backbone router that you intend to configure.

Step 6

ip cef accounting non-recursive {external | internal}

Example:

Router(config-if)# ip cef accounting non-recursive external

Enables nonrecursive accounting on the router.

- The external keyword calls for a count of input traffic data in the nonrecursive external bin.

That is, this keyword sets the specified incoming interface so that it can collect data on traffic entering the backbone router from external sources.

- The internalkeyword calls for a count of input traffic data in the nonrecursive internal bin.

That is, this keyword sets the specified incoming interface so that it can collect data on internal traffic in the backbone router.

Step 7

exit

Example:

Router(config-if)# exit

Exits to privileged EXEC mode.

Step 8

Repeat Steps 5, 6, and 7 for each incoming interface that you want to configure for TMS.

--

Enabling the NDA to Collect TMS on a Backbone Router

Perform the following task to enable the NDA to collect TMS on a backbone router.

You can use the NDA to enable TMS collection and to set the incoming interfaces on the backbone router to collect internal or external traffic data.

SUMMARY STEPS

1.    Open the Traffic Matrix Statistics Control window in the NDA.

2.    Click the New button in the Traffic Matrix Statistics Control window.

3.    Specify the new TMS collection parameters, using the Traffic Matrix Statistics Control window.

4.    Click OK in the New Collection panel.

5.    Select the TMS tab in the Router Configuration window in the NDA.

6.    Set internal and external interfaces on the router.

7.    Click Applyin the Router Configuration window.

DETAILED STEPS

Step 1

Open the Traffic Matrix Statistics Control window in the NDA.
For specific instructions, see the Network Data Analyzer Installation and User Guide .

Step 2

Click the New button in the Traffic Matrix Statistics Control window.
If a valid directory of router configuration files exists on a designated Utility Server host in the network, the Traffic Matrix Statistics Control window shown in the figure below appears.

Step 3

Specify the new TMS collection parameters, using the Traffic Matrix Statistics Control window.
The window incorporates a New Collection panel that enables you to define a new TMS collection process. To use the NDA for TMS collection, you must specify the following information:

- The name of the collection (Collection ID)--Enter an alphanumeric name of any length without embedded spaces for the TMS collection process on the selected router (see next bullet).

- The router from which you want to collect TMS--Use the drop-down box to choose the name of a network device where you want to collect TMS.

- How often and how long to collect TMS--Specify each of the following in minutes:

- How much time is to elapse before the TMS collection process begins ("Start in" field)

- The overall duration of the TMS collection process ("collect for" field)

- How often "snapshots" of the traffic counters in the selected router are to be exported to the designated TMS data repository ("every" field)

The window for entering this information on the NDA is similar to the one shown in the figure below.

Setting the NDA Traffic Matrix Statistics Control Window Collection Parameters

Step 4

Click OK in the New Collection panel.
The Traffic Matrix Statistics Control window confirms the information you entered, and the new collection name appears at the top left corner of the window.

Step 5

Select the TMS tab in the Router Configuration window in the NDA.
The TMS Router Configuration panel shown in the figure below appears. This panel enables you to configure network devices to export TMS data. (For instructions on locating the Router Configuration window, see the Network Data Analyzer Installation and User Guide .)

Step 6

Set internal and external interfaces on the router.
The Router Configuration window allows you to set the interfaces on the backbone router to collect internal and external packet and byte data. By default, all interfaces are set to collect internal data. Single-selection buttons allow you to associate the interface with either internal data or external data. You can select only one radio button for an interface at one time. Set the interface to collect internal or external data by clicking the appropriate radio button.

The window for selecting this information on the NDA is similar to the one shown in the figure below.

Setting the NDA Configuration Window

Step 7

Click Applyin the Router Configuration window.
Any changes that you have made to the configuration parameters in the TMS Router Configuration panel are applied to the currently selected device. The Apply button affects only changes made in the panel where the button is located. When the NDA asks if you want to enable Cisco Express Forwarding, click Yes.

Interpreting the tmstats File

This section contains instructions for interpreting the statistics in the tmstats_ascii file. For conceptual information about the tmstats_ascii file, see the Statistics in the timestats File.

SUMMARY STEPS

1.    more system:/vfiles/tmstats_ascii

2.    Interpret the header and record information in the tmstats_ascii file.

DETAILED STEPS

Step 1

more system:/vfiles/tmstats_ascii

Enter this command on the backbone router to view the statistics in the ASCII file. For example:

Example:

Router# more system:/vfiles/tmstats_ascii
VERSION 1|ADDR 172.27.32.24|AGGREGATION TrafficMatrix.ascii|SYSUPTIME 41428|routerUTC 3104467160|NTP unsynchronized|DURATION 1|
p|10.1.0.0/16|242|1|50|2|100
p|172.27.32.0/22|242|0|0|0|0

This is an example of a tmstats_ascii file. The example contains a header information and two records. The header information and each record begin on a separate line. A bar (|) separates consecutive fields within a header or record. The first field in a record specifies the type of record.

Step 2

Interpret the header and record information in the tmstats_ascii file.
Each tmstats_ascii file displayed consists of header information and records. The file in the example in Step 1 contains header information and two destination prefix records.

See thefollowing sections for a description of header and record information:

Viewing Information in the tmsasinfo File

Perform the following task to view information in the tmsasinfo file about BGP neighbor autonomous systems (ASs) for IGP destinations.

The TMS feature also displays the BGP neighbor ASs associated with each IGP destination. You can display all the neighbor ASs for any IGP destination. The tmsasinfo file is in ASCII format. It is the only format provided for this data.

For conceptual information about the tmsasinfo file, see the Statistics in the tmsasinfo File.

SUMMARY STEPS

1.    more system:/vfiles/tmsasinfo

2.    View the header and record information in the tmasinfo file.

DETAILED STEPS

Step 1

more system:/vfiles/tmsasinfo

Enter this command on the backbone router to view the statistics in the tmsasinfo ASCII file. For example:

Example:

Router# more system:/vfiles/tmsasinfo

VERSION 1|ADDR 10.10.10.10|AGGREGATION ASList.ascii|SYSUPTIME 619855|routerUTC 3334075555|DURATION 0
10.1.1.2/32|65535|192.168.1.0/24
This is an example of a tmsasinfo file. The example contains a header information and one record. The header information and each record begin on a separate line. A bar (|) separates consecutive fields within a header or record.

Step 2

View the header and record information in the tmasinfo file.
See the following sections for a description of header and record information:

Verifying CEF Network Accounting Information

Perform the following task to verify that Cisco Express Forwarding networking accounting information is as you expected.

SUMMARY STEPS

1.    show ip cef summary

2.    show ip cef interface - type number detail

DETAILED STEPS

Step 1

show ip cef summary

Use this command to display the collected Cisco Express Forwarding network accounting information. For example:

Example:

Router# show ip cef summary
IP CEF with switching (Table Version 19), flags=0x0
19 routes, 0 reresolve, 0 unresolved (0 old, 0 new), peak 1
19 leaves, 17 nodes, 19960 bytes, 58 inserts, 39 invalidations
0 load sharing elements, 0 bytes, 0 references
universal per-destination load sharing algorithm, id E3296D5B
3(1) CEF resets, 0 revisions of existing leaves
Resolution Timer: Exponential (currently 1s, peak 1s)
0 in-place/0 aborted modifications
refcounts:  4628 leaf, 4608 node
Adjacency Table has 7 adjacencies

This command shows sample accounting information on a router with Central Cisco Express Forwarding enabled. In this example, the Cisco Express Forwarding table contains a total or 19 entries, 0 entries need to be reresolved, 0 entries do not have resolved recursions, and the highest number of unresolved entries is 1. The Cisco Express Forwarding Trie contains 19 leaves and 17 nodes, which take up 19960 bytes of memory. The number of routes inserted into the table is 58 and 39 routes have been invalidated. This command shows no load sharing elements. The per-destination load sharing algorithm is configured and the identifier is E3296D5D.

The following command is sample output for a router with distributed Cisco Express Forwarding enabled:

Example:

Router# show ip cef summary
IP Distributed CEF with switching (Table Version 36), flags=0x0
16 routes, 0 reresolve, 0 unresolved (0 old, 0 new), peak 1
19 leaves, 17 nodes, 19960 bytes, 39 inserts, 20 invalidations
0 load sharing elements, 0 bytes, 0 references
universal per-destination load sharing algorithm, id E3296D5B
2(0) CEF resets, 0 revisions of existing leaves
Resolution Timer: Exponential (currently 1s, peak 1s)
0 in-place/0 aborted modifications
refcounts:  4628 leaf, 4608 node

Step 2

show ip cef interface - type number detail

Use this command to show detailed Cisco Express Forwarding network accounting information for a specified interface type and number. The following is sample output from the show ip cef detailcommand for interface Ethernet 0. It shows all the prefixes resolving through adjacency pointing to next hop interface Ethernet 0/0 and next hop interface IP address 172.29.233.33.

For example, for Ethernet interface 0, IP address 172.29.233.33:

Example:

Router# show ip cef ethernet 0/0 detail
IP Distributed CEF with switching (Table Version 136808)
45800 routes, 8 unresolved routes (0 old, 8 new)
45800 leaves, 2868 nodes, 8444360 bytes,
136808 inserts, 91008 invalidations
1 load sharing elements, 208 bytes, 1 references
1 CEF resets, 1 revisions of existing leaves
refcounts: 527343 leaf, 465638 node
172.29.233.33/32, version 7417, cached adjacency 172.29.233.33
0 packets, 0 bytes,
Adjacency-prefix
via 172.29.233.33, Ethernet0/0, 0 dependencies
next hop 172.29.233.33, Ethernet0/0
valid cached adjacency
0 packets, 0 bytes switched through the prefix
tmstats: external 0 packets, 0 bytes
internal 0 packets, 0 bytes

Configuration Examples for CEF Network Accounting

- Example Configuring CEF Network Accounting

- Example Enabling a Backbone Router to Collect TMS Data

- Example IP CEF Nonrecursive Accounting

- Example Interpreting the tmstats_ascii File

Example Configuring CEF Network Accounting

The following example shows how to enable the collection of Cisco Express Forwarding accounting information:

configure terminal
!
ip cef accounting
end

Example Enabling a Backbone Router to Collect TMS Data

The following example shows how to enable a backbone router to collect TMS data:

configure terminal
!
ip cef
ip cef accounting non-recursive
!
interface e1/0
ip cef accounting non-recursive external
end

For a sample backbone configuration, see the Example IP CEF Nonrecursive Accounting section.

Example IP CEF Nonrecursive Accounting

The following example shows an IP Cisco Express Forwarding accounting configuration. The example shows how to enable routers to count the number of internal and external packets and bytes that travel through the backbone routers. The figure below shows the sample backbone configuration.

Sample Backbone Configuration

Router A Configuration

Router(config)# ip cef
Router(config)# ip cef accounting non-recursive
Router(config)# interface e1/0
Router(config-if)# ip cef accounting non-recursive external

Router B Configuration: e1/1

Router(config)# ip cef
Router(config)# ip cef accounting non-recursive
Router(config)# interface e1/1

Router(config-if)# ip cef accounting non-recursive external

Router B Configuration: e1/0

Router(config)# interface e1/0
Router(config-if)# ip cef accounting non-recursive internal

Router C Configuration: e1/1:

Router(config)# ip cef
Router(config)# ip cef accounting non-recursive
Router(config)# interface e1/1

Router(config-if)# ip cef accounting non-recursive internal

Router C Configuration: e1/0

Router(config)# interface e1/0
Router(config-if)# ip cef accounting non-recursive external

Router D Configuration

Router(config)# ip cef
Router(config)# ip cef accounting non-recursive
Router(config)# interface e1/1

Router(config-if)# ip cef accounting non-recursive external

Example Interpreting the tmstats_ascii File

The following example shows the contents of tmstats_ascii file:

Router# more system:/vfiles/tmstats_ascii
VERSION 1|ADDR 172.27.32.24|AGGREGATION TrafficMatrix.ascii|SYSUPTIME 41428|routerUTC 3104467160|NTP unsynchronized|DURATION 1|
p|10.1.0.0/16|242|1|50|2|100
p|172.27.32.0/22|242|0|0|0|0

This example contains header information and two destination prefix records. The records represent dynamic label switching or traffic engineering (TE) tunnel data indicated by the initial "p."

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

IP switching commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples.

Cisco IOS IP Switching Command Reference

Overview of the Cisco Express Forwarding feature

Cisco Express Forwarding Overview

Tasks for verifying basic Cisco Express Forwarding and distributed Cisco Express Forwarding operation

Configuring Basic Cisco Express Forwarding for Improved Performance, Scalability, and Resiliency in Dynamic Networks

Tasks for enabling or disabling Cisco Express Forwarding or distributed Cisco Express Forwarding

Enabling or Disabling Cisco Express Forwarding or Distributed Cisco Express Forwarding to Customize Switching and Forwarding for Dynamic Networks

Tasks for configuring load-balancing schemes for Cisco Express Forwarding

Configuring a Load-Balancing Scheme for Cisco Express Forwarding Traffic

Tasks for configuring Cisco Express Forwarding consistency checkers

Configuring Cisco Express Forwarding Consistency Checkers for Route Processors and Line Cards

Tasks for configuring epochs for Cisco Express Forwarding tables

Configuring Epochs to Clear and Rebuild Cisco Express Forwarding and Adjacency Tables

Tasks for customizing the display of recorded Cisco Express Forwarding events

Customizing the Display of Recorded Cisco Express Forwarding Events

How to determine which Cisco IOS switching or forwarding path your packets are taking

How to Verify Cisco Express Forwarding Switching

How to use the Cisco Network Data Analyzer to view TMS

Network Data Analyzer Installation and User Guide

Commands for configuring and monitoring Cisco Express Forwarding

Cisco IOS IP Switching Command Reference

Standards

Standard

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

--

MIBs

MIB

MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

Click Here

RFCs

RFC

Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

--

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

Click Here

Feature Information for CEF Network Accounting

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.

Feature Information for Configuring Cisco Express Forwarding Network Accounting

Feature Name

Releases

Feature Configuration Information

This table is intentionally left blank because no features were introduced or modified in Cisco IOS Release 12.2(1) or later.

--

--

Glossary

AS --autonomous system. A collection of networks under a common administration sharing a common routing strategy. Autonomous systems are subdivided by areas. An autonomous system must be assigned a unique 16-bit number by the Internet Assigned Numbers Authority (IANA).

adjacency --A relationship formed between selected neighboring routers and end nodes for the purpose of exchanging routing information. Adjacency is based upon the use of a common media segment by the routers and nodes involved.

BGP --Border Gateway Protocol. An interdomain routing protocol that replaces Exterior Gateway Protocol (EGP). BGP exchanges reachability information with other BGP systems. It is defined by RFC 1163.

Cisco Express Forwarding --A Layer 3 switching technology. Cisco Express Forwarding can also refer to central Cisco Express Forwarding mode, one of two modes of Cisco Express Forwarding operation. Cisco Express Forwarding enables a Route Processor to perform express forwarding. Distributed Cisco Express Forwarding is the other mode of Cisco Express Forwarding operation.

distributed Cisco Express Forwarding --A type of Cisco Express Forwarding switching in which line cards (such as Versatile Interface Processor (VIP) line cards) maintain identical copies of the Forwarding Information Base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters; this relieves the Route Switch Processor of involvement in the switching operation.

FIB --forwarding information base. A component of Cisco Express Forwarding. The router uses the FIB lookup table to make destination-based switching decisions during Cisco Express Forwarding operation. The router maintains a mirror image of the forwarding information in an IP routing table.

IGP -- Interior Gateway Protocol. An internet protocol used to exchange routing information within an autonomous system. Examples of common Internet IGPs include Interior Gateway Routing Protocol (IGRP), Open Shortest Path First (OSPF), and Routing Information Protocol (RIP).

label --A short fixed-length data construct that tells switching nodes how to forward data (packets or cells).

line card --A general term for an interface processor that can be used in various Cisco products. For example, a Versatile Interface Processor (VIP) is a line card for the Cisco 7500 series router.

prefix --The network address portion of an IP address. A prefix is specified by a network and mask and is generally represented in the format network/mask. The mask indicates which bits are the network bits. For example, 1.0.0.0/16 means that the first 16 bits of the IP address are masked, making them the network bits. The remaining bits are the host bits. In this example, the network number is 10.0.

RP --Route Processor. The processor module in the Cisco 7000 series routers that contains the CPU, system software, and most of the memory components that are used in the router. It is sometimes called a supervisory processor.

TE --traffic engineering. Techniques and processes that cause routed traffic to travel through the network on a path other than the one that would have been chosen if standard routing methods were used.

traffic engineering tunnel --A label-switched tunnel that is used for traffic engineering. Such a tunnel is set up through means other than normal Layer 3 routing; it is used to direct traffic over a path different from the one that Layer 3 routing could cause the tunnel to take.

TMS --Traffic Matrix Statistics. An IOS feature that enables an administrator to capture and analyze traffic data entering a backbone that is running the Border Gateway Protocol (BGP). This feature also allows an administrator to determine the neighbor autonomous systems of a BGP destination

VPN --Virtual Private Network. The result of a router configuration that enables IP traffic to use tunneling to travel securely over a public TCP/IP network.

VRF --A Virtual Private Network (VPN) routing/forwarding instance. A VRF consists of an IP routing table, a derived forwarding table, a set of interfaces that use the forwarding table, and a set of rules and routing protocols that determine what goes into the forwarding table. In general, a VRF includes the routing information that defines a customer VPN site that is attached to a PE router.

Chapter 8. Customizing the Display of Recorded CEF Events

This module contains information about and instructions for customizing the display of recorded Cisco Express Forwarding events for Cisco IOS releases prior to 12.2(25)S, 12.2(33)SB, 12.2(33)SRA, 12.2.(33)SXH, and 12.4(20)T.

For information about and instructions for customizing the display of recorded Cisco Express Forwarding events for Cisco IOS Releases 12.2(25)S, 12.2(33)SB, 12.2(33)SRA, 12.2.(33)SXH, 12.4(20)T, and later releases, see Customizing the Display of Cisco IOS Event Trace Messages.

You can customize the Cisco Express Forwarding event log display by specifying the size of the Cisco Express Forwarding event log or by choosing to display events by prefix and mask or by Cisco Express Forwarding Virtual Private Network (VPN) routing/forwarding instance (VRF).

Cisco Express Forwarding is an advanced Layer 3 IP switching technology. It optimizes network performance and scalability for all kinds of networks: those that carry small amounts of traffic and those that carry large amounts of traffic in complex patterns, such as the Internet and networks characterized by intensive web-based applications or interactive sessions.

- Finding Feature Information

- Prerequisites for the Display of Recorded CEF Events

- Restrictions for the Display of Recorded CEF Events

- Information About the Display of Recorded CEF Events

- How to Customize the Display of Recorded CEF Events

- Configuration Examples for the Display of Recorded CEF Events

- Additional References

- Feature Information for the Display of Recorded CEF Events

- Glossary

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to Click Here . An account on Cisco.com is not required.

Prerequisites for the Display of Recorded CEF Events

Cisco Express Forwarding must be running on the networking device before you can customize the display of recorded Cisco Express Forwarding events.

Restrictions for the Display of Recorded CEF Events

If you enable Cisco Express Forwarding and then create an access list that uses the log keyword, the packets that match the access list are not Cisco Express Forwarding switched. They are fast switched. Logging disables Cisco Express Forwarding.

Information About the Display of Recorded CEF Events

For links to information about other Cisco Express Forwarding and distributed Cisco Express Forwarding features that you can configure, go to the Additional References.

- Cisco Platform Support for Central CEF and dCEF

- CEF Event Log Overview

Cisco Platform Support for Central CEF and dCEF

Cisco Express Forwarding is enabled by default on most Cisco platforms running Cisco IOS software Release 12.0 or later. When Cisco Express Forwarding is enabled on a router, the Route Processor (RP) performs the express forwarding.

To find out if Cisco Express Forwarding is enabled on your platform, enter the show ip cefcommand. If Cisco Express Forwarding is enabled, you receive output that looks like this:

Router# show ip cef
Prefix              Next Hop            Interface
[...]
10.2.61.8/24        192.168.100.1       FastEthernet1/0/0
192.168.101.1       FastEthernet6/1
[...]

If Cisco Express Forwarding is not enabled on your platform, the output for the show ip cefcommand looks like this:

Router# show ip cef
%CEF not running

Distributed Cisco Express Forwarding is enabled by default on the Catalyst 6500 series switch, the Cisco 7500 series router, and the Cisco 12000 Series Internet Router. When distributed Cisco Express Forwarding is enabled on your platform, the line cards perform the express forwarding.

If Cisco Express Forwarding is not enabled on your platform, use the ip cef command to enable (central) Cisco Express Forwarding or the ip cef distributed command to enable distributed Cisco Express Forwarding.

CEF Event Log Overview

The Cisco Express Forwarding event log collects Cisco Express Forwarding events as they occur, even when debugging is not enabled. This allows the tracing of an event immediately after it occurs. Cisco technical personnel can use the event log to help resolve problems with the Cisco Express Forwarding feature.

When the Cisco Express Forwarding event log has reached its capacity, the oldest event is written over by the newest event. You can use the following commands to change the capacity of the Cisco Express Forwarding event log:

- The ip cef table event-logcommand allows you to increase or decrease the number of entries that the event log can hold.

- The clear ip cef event-log command allows you to clear all event log entries.

You can use the following commands to display Cisco Express Forwarding events:

- The show ip cef eventscommand displays all recorded Cisco Express Forwarding forwarding information base (FIB) and adjacency events.

- The debug ip cef command and the events keyword record general Cisco Express Forwarding events as they occur.

- The debug ip cef tablecommand enables the real-time collection of events that affect entries in the Cisco Express Forwarding tables.

How to Customize the Display of Recorded CEF Events

- Customizing CEF Event Logging

- Displaying CEF Event-Log Information

Customizing CEF Event Logging

This section contains information about and instructions for customizing Cisco Express Forwarding event logging.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ip cef table event-log [size event-number] [match ip-prefix mask] [vrf vrf-name]

4.    exit

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

ip cef table event-log [size event-number] [match ip-prefix mask] [vrf vrf-name]

Example:

Router(config)# ip cef table event-log size 25000

Controls Cisco Express Forwarding table event-log characteristics.

- The size event-number keyword-argument pair specifies the number of event entries. The range is from 1 to 4294967295.

- The match keyword logs events that match the specified prefix and mask.

- The ip-prefix argument is the specified IP prefix to match in dotted decimal format (A.B.C.D).

- The mask argument is the network mask written as A.B.C.D.

- The vrf vrf-name keyword-argument pair displays the named Virtual Private Network (VPN) routing/forwarding instance (VRF) Cisco Express Forwarding table.

Step 4

exit

Example:

Router(config)# exit

Exits to privileged EXEC mode.

Displaying CEF Event-Log Information

Perform the following task to display Cisco Express Forwarding event-log information.

SUMMARY STEPS

1.    enable

2.    clear ip cef event-log

3.    debug ip cef table

4.    show ip cef events summary

5.    show ip cef events within seconds

6.    exit

DETAILED STEPS

Step 1

enable

Use this command to enable privileged EXEC mode. For example:

Example:

Router> enable

Enter your password if prompted.

Step 2

clear ip cef event-log

Use this command to clear the Cisco Express Forwarding event-log buffer. For example:

Router# clear ip cef event-log

Example:

Step 3

debug ip cef table

Use this command to enable the collection of events that affect entries in the Cisco Express Forwarding tables. For example:

Example:

Router# debug ip cef table
01:25:46:CEF-Table:Event up, 10.1.1.1/32 (rdbs:1, flags:1000000)
01:25:46:CEF-IP:Checking dependencies of 0.0.0.0/0
01:25:47:CEF-Table:attempting to resolve 10.1.1.1/32
01:25:47:CEF-IP:resolved 10.1.1.1/32 via 10.9.104.1 to 10.9.104.1 Ethernet2/0/0
01:26:02:CEF-Table:Event up, default, 0.0.0.0/0 (rdbs:1, flags:400001)
01:26:02:CEF-IP:Prefix exists - no-op change

Step 4

show ip cef events summary

Use this command to display a summary of recorded Cisco Express Forwarding FIB and adjacency events. For example:

Example:

Router# show ip cef events summary
CEF table events summary:
Storage for 10000 events (320000 bytes), 822/0 events recorded/ignored
Matching all events, traceback depth 16
Last event occurred 00:00:06.516 ago.

Step 5

show ip cef events within seconds

Use this command to display Cisco Express Forwarding events that occurred within (during) a specified number of seconds. For example, within 1 second:

Example:

Router# show ip cef events within 1
CEF table events (storage for 10000 events, 14 events recorded)
+00:00:00.000:[Default-table] *.*.*.*/*           New FIB table          [OK]
+00:00:00.000:[Default-table] 10.1.80.194/32      FIB insert in mtrie    [OK]
+00:00:00.000:[Default-table] 10.1.80.0/32        FIB insert in mtrie    [OK]
+00:00:00.000:[Default-table] 10.1.80.255/32      FIB insert in mtrie    [OK]
+00:00:00.004:[Default-table] 10.1.80.0/24        FIB insert in mtrie    [OK]
+00:00:00.004:[Default-table] 10.1.80.0/24        NBD up                 [OK]
+00:00:00.004:[Default-table] 239.224.0.0/4       FIB insert in mtrie    [OK]
+00:00:00.012:[Default-table] 10.1.80.0/24        NBD up                 [Ignr]
+00:00:00.012:[Default-table] 239.224.0.0/4       FIB remove             [OK]
+00:00:00.016:[Default-table] 239.224.0.0/4       FIB insert in mtrie    [OK]
+00:00:05.012:[Default-table] 239.224.0.0/4       FIB remove             [OK]
+00:00:05.012:[Default-table] 239.224.0.0/4       FIB insert in mtrie    [OK]
+00:00:28.440:[Default-table] 239.224.0.0/4       FIB remove             [OK]
+00:00:28.440:[Default-table] 239.224.0.0/4       FIB insert in mtrie    [OK]
First event occured at 00:00:36.568 (00:04:40.756 ago)
Last event occured at 00:01:05.008 (00:04:12.316 ago)

Step 6

exit

Use this command to exit to user EXEC mode. For example:

Example:

Router# exit
Router>

Configuration Examples for the Display of Recorded CEF Events

- Example Customizing CEF Event Logging

Example Customizing CEF Event Logging

The following example shows how to enable event logging for Cisco Express Forwarding:

clear ip cef event-log
!
debug ip cef table
!
configure terminal
!
ip cef table event-log size 25000
exit
!

In this example, the Cisco Express Forwarding event log is configured to hold 25000 entries.

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

Cisco Express Forwarding commands

Cisco IOS IP Switching Command Reference

Overview of the Cisco Express Forwarding feature

Cisco Express Forwarding Overview

Tasks for verifying basic Cisco Express Forwarding and distributed Cisco Express Forwarding operation

Configuring Basic Cisco Express Forwarding for Improved Performance, Scalability, and Resiliency in Dynamic Networks

Tasks for enabling or disabling Cisco Express Forwarding or distributed Cisco Express Forwarding

Enabling or Disabling Cisco Express Forwarding or Distributed Cisco Express Forwarding to Customize Switching and Forwarding for Dynamic Networks

Tasks for configuring load-balancing schemes for Cisco Express Forwarding

Configuring a Load-Balancing Scheme for Cisco Express Forwarding Traffic

Tasks for configuring Cisco Express Forwarding consistency checkers

Configuring Cisco Express Forwarding Consistency Checkers for Route Processors and Line Cards

Tasks for configuring epochs for Cisco Express Forwarding tables

Configuring Epochs to Clear and Rebuild Cisco Express Forwarding and Adjacency Tables

Tasks for configuring and verifying Cisco Express Forwarding network accounting

Configuring Cisco Express Forwarding Network Accounting

Tasks for customizing the display of recorded Cisco Express Forwarding events trace messages for Cisco IOS Releases 12.2(25)S, 12.2(33)SB, 12.2(33)SRA, 12.2.(33)SXH, 12.4(20)T and later releases

Customizing the Display of Cisco IOS Event Trace Messages

Causes of common Cisco Express Forwarding-related error messages on platforms running distributed Cisco Express Forwarding switching (Cisco 7500 series routers and Cisco 12000 series Internet routers) and how to troubleshoot them

Troubleshooting Cisco Express Forwarding-Related Error Messages

Standards

Standards

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

--

MIBs

MIBs

MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

Click Here

RFCs

RFCs

Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

--

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

Click Here

Feature Information for the Display of Recorded CEF Events

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.

Feature Information for Configuring the Display of Recorded Cisco Express Forwarding Events

Feature Name

Releases

Feature Configuration Information

This table is intentionally left blank because no features were introduced or modified in Cisco IOS Release 12.2(1) or later. This table will be updated when feature information is added to this module.

--

--

Glossary

adjacency --A relationship formed between selected neighboring routers and end nodes for the purpose of exchanging routing information. Adjacency is based upon the use of a common media segment by the routers and nodes involved.

Cisco Express Forwarding --A Layer 3 switching technology. Cisco Express Forwarding can also refer to central Cisco Express Forwarding mode, one of two modes of Cisco Express Forwarding operation. Cisco Express Forwarding enables a Route Processor to perform express forwarding. Distributed Cisco Express Forwarding is the other mode of Cisco Express Forwarding operation.

distributed Cisco Express Forwardin g--A mode of Cisco Express Forwarding operation in which line cards (such as Versatile Interface Processor (VIP) line cards) maintain identical copies of the forwarding information base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters; this relieves the Route Switch Processor of involvement in the switching operation.

FIB --forwarding information base. A component of Cisco Express Forwarding that is conceptually similar to a routing table or information base. The router uses the FIB lookup table to make destination-based switching decisions during Cisco Express Forwarding operation. The router maintains a mirror image of the forwarding information in an IP routing table.

line card --A general term for an interface processor that can be used in various Cisco products. For example, a Versatile Interface Processor (VIP) is a line card for the Cisco 7500 series router.

prefix --The network address portion of an IP address. A prefix is specified by a network and mask and is generally represented in the format network/mask. The mask indicates which bits are the network bits. For example, 1.0.0.0/16 means that the first 16 bits of the IP address are masked, making them the network bits. The remaining bits are the host bits. In this example, the network number is 10.0.

VPN --Virtual Private Network. The result of a router configuration that enables IP traffic to use tunneling to travel securely over a public TCP/IP network.

VRF --A Virtual Private Network (VPN) routing/forwarding instance. A VRF consists of an IP routing table, a derived forwarding table, a set of interfaces that use the forwarding table, and a set of rules and routing protocols that determine what goes into the forwarding table. In general, a VRF includes the routing information that defines a customer VPN site that is attached to a PE router.

Chapter 9. Customizing the Display of CEF Event Trace Messages

This module contains information about and instructions for customizing the display of recorded Cisco Express Forwarding events for Cisco IOS Releases 12.2(25)S, 12.2(33)SB, 12.2(33)SRA, 12.2.(33)SXH, 12.4(20)T, and later releases.

For information about and instructions for customizing the display of recorded Cisco Express Forwarding events for Cisco IOS releases prior to 12.2(25)S, 12.2(33)SB, 12.2(33)SRA, 12.2.(33)SXH, and 12.4(20)T, see Customizing the Display of Cisco Express Forwarding Events.

You can customize the Cisco Express Forwarding event-tracing message display by specifying the size of the file stored in memory or by choosing to display event trace messages by prefix and mask, by a specified interface, or by a Cisco Express Forwarding Virtual Private Network (VPN) routing and forwarding instance (VRF) for an IPv4 or IPv6 address family.

Cisco Express Forwarding is an advanced Layer 3 IP switching technology. It optimizes network performance and scalability for all kinds of networks: those that carry small amounts of traffic and those that carry large amounts of traffic in complex patterns, such as the Internet and networks characterized by intensive web-based applications or interactive sessions.

- Finding Feature Information

- Prerequisites for the Display of CEF Event Trace Messages

- Restrictions for the Display of CEF Event Trace Messages

- Information About the Display of CEF Event Trace Messages

- How to Customize the Display of CEF Event Trace Messages

- Configuration Examples for the Display of CEF Event Trace Messages

- Additional References

- Feature Information for the Display of CEF Event Trace Messages

- Glossary

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to Click Here . An account on Cisco.com is not required.

Prerequisites for the Display of CEF Event Trace Messages

Cisco Express Forwarding must be running on the networking device before you can customize the display of recorded Cisco Express Forwarding events.

Restrictions for the Display of CEF Event Trace Messages

If you enable Cisco Express Forwarding and then create an access list that uses the log keyword, the packets that match the access list are not Cisco Express Forwarding switched. They are fast switched. Logging disables Cisco Express Forwarding.

Information About the Display of CEF Event Trace Messages

For links to information about other Cisco Express Forwarding and distributed Cisco Express Forwarding features that you can configure, go to the Additional References.

- Cisco Platform Support for Central CEF and dCEF

- Overview of CEF Event Trace Function

- CEF Event Tracing Defaults and Options

Cisco Platform Support for Central CEF and dCEF

Cisco Express Forwarding is enabled by default on most Cisco platforms running Cisco IOS software Release 12.0 or later. When Cisco Express Forwarding is enabled on a router, the Route Processor (RP) performs the express forwarding.

To find out if Cisco Express Forwarding is enabled on your platform, enter the show ip cefcommand. If Cisco Express Forwarding is enabled, you receive output that looks like this:

Router# show ip cef
Prefix              Next Hop            Interface
[...]
10.2.61.8/24        192.168.100.1       FastEthernet1/0/0
192.168.101.1       FastEthernet6/1
[...]

If Cisco Express Forwarding is not enabled on your platform, the output for the show ip cefcommand looks like this:

Router# show ip cef
%CEF not running

Distributed Cisco Express Forwarding is enabled by default on the Catalyst 6500 series switch, the Cisco 7500 series router, and the Cisco 12000 Series Internet Router. When distributed Cisco Express Forwarding is enabled on your platform, the line cards perform the express forwarding.

If Cisco Express Forwarding is not enabled on your platform, use the ip cefcommand to enable (central) Cisco Express Forwarding or the ip cef distributed command to enable distributed Cisco Express Forwarding.

Overview of CEF Event Trace Function

The Cisco Express Forwarding event trace function collects Cisco Express Forwarding events as they occur, even when debugging is not enabled. This function allows the tracing of an event immediately after it occurs. Cisco technical personnel can use the event trace function to help resolve any problems with the Cisco Express Forwarding feature.

Cisco Express Forwarding event trace messages are saved in memory on the device. When the event trace messages exceed the configured size, the newest message in the trace will begin to overwrite the older messages. You can use the following commands to change the capacity of the Cisco Express Forwarding event message file:

- The monitor event-trace cef events sizeglobal configuration command allows you to increase or decrease the number of messages that can be written to memory for a single instance of a trace. To display the size parameter, use the show monitor event-trace events parameters command.

- The monitor event-trace cef events clear privileged EXEC command allows you to clear existing trace messages.

- The monitor event-trace cef(global) command configures event tracing for Cisco Express Forwarding events. To monitor and control the event trace function for Cisco Express Forwarding events, use the monitor event-trace cef (EXEC) command.

You can use the following commands to display Cisco Express Forwarding events:

- The show monitor event-trace cef allcommand displays all event trace messages currently in memory for Cisco Express Forwarding.

- The debug ip cef command and the events keyword record general Cisco Express Forwarding events as they occur.

- The debug ip cef tablecommand enables the real-time collection of events that affect entries in the Cisco Express Forwarding tables.

CEF Event Tracing Defaults and Options

Event tracing for distributed Cisco Express Forwarding events is enabled by default. The Cisco IOS XE software allows Cisco Express Forwarding to define whether support for event tracing is enabled or disabled by default. The command interface for event tracing allows you to change the default value in one of two ways: using the monitor event-trace cefcommand in privileged EXEC mode or using the monitor event-trace cefcommand in global configuration mode.

To configure the file in which you want to save trace information, use the monitor event-trace cefcommand in global configuration mode. By default, the trace messages are saved in a binary format. If you want to save trace messages in ASCII format, possibly for additional application processing, use the monitor event-trace cef dump pretty command in privileged EXEC mode. The amount of data collected from a trace depends on the trace message size configured using the monitor event-trace cefcommand in global configuration mode for each instance of a trace.

To specify the trace call stack at tracepoints, you must first clear the trace buffer.

- CEF Event Tracing for IPv4 Events

- CEF Event Tracing for IPv6 Events

CEF Event Tracing for IPv4 Events

Event tracing for Cisco Express Forwarding IPv4 events is enabled by default. The software allows Cisco Express Forwarding to define whether support for event tracing is enabled or disabled by default. The command interface for event tracing allows you to change the default value in one of two ways: using the monitor event-trace cef ipv4command in privileged EXEC mode or using the monitor event-trace cef ipv4command in global configuration mode.

To configure the file in which you want to save trace information for Cisco Express Forwarding IPv4 events, use the monitor event-trace cef ipv4command in global configuration mode. By default, the trace messages are saved in a binary format. If you want to save trace messages in ASCII format, possibly for additional application processing, use the monitor event-trace cef ipv4 dump pretty command in privileged EXEC mode. The amount of data collected from the trace depends on the trace message size configured using the monitor event-trace cef ipv4command for each instance of a trace.

To determine whether event tracing is enabled by default for Cisco Express Forwarding, use the show monitor event-trace cef ipv4command to display trace messages.

To specify the trace call stack at tracepoints, you must first clear the trace buffer.

CEF Event Tracing for IPv6 Events

Event tracing for Cisco Express Forwarding IPv6 events is enabled by default.The Cisco IOS XE software allows Cisco Express Forwarding to define whether support for event tracing is enabled or disabled by default. The command interface for event tracing allows you to change the default value in one of two ways: using the monitor event-trace cef ipv6command in privileged EXEC mode or using the monitor event-trace cef ipv6command in global configuration mode.

To configure the file in which you want to save trace information for Cisco Express Forwarding IPv6 events, use the monitor event-trace cef ipv6command in global configuration mode. By default, the trace messages are saved in a binary format. If you want to save trace messages in ASCII format, possibly for additional application processing, use the monitor event-trace cef ipv6 dump pretty command in privileged EXEC mode. The amount of data collected from the trace depends on the trace message size configured using the monitor event-trace cef ipv6command for each instance of a trace.

To determine whether event tracing is enabled by default for Cisco Express Forwarding, use the show monitor event-trace cef ipv6command to display trace messages.

To specify the trace call stack at tracepoints, you must first clear the trace buffer.

How to Customize the Display of CEF Event Trace Messages

- Customizing CEF Event Tracing

- Customizing CEF Event Tracing for IPv4 Events

- Customizing CEF Event Tracing for IPv6 Events

- Displaying CEF Event Trace Information

Customizing CEF Event Tracing

Perform the following task to customize Cisco Express Forwarding event tracing. Event trace messages can be used to monitor Cisco Express Forwarding and to help resolve any issues with the Cisco Express Forwarding feature.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    monitor event-trace cef {dump-file dump-file-name | {events | interface} {disable | dump-file dump-file-name| enable | size number | stacktrace [depth]}}

4.    exit

5.    monitor event-trace cef {dump [merged pretty | pretty] | {events | interface | ipv4 | ipv6} {clear | continuous [cancel] | disable | dump [pretty] | enable | one-shot}}

6.    disable

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

monitor event-trace cef {dump-file dump-file-name | {events | interface} {disable | dump-file dump-file-name| enable | size number | stacktrace [depth]}}

Example:

Router(config)# monitor event-trace cef dump-file tftp://172.16.10.5/cef-events

Configures event tracing for Cisco Express Forwarding.

- The dump-file dump-file-name keyword and argument pair specify the file to which event trace messages are written from memory on the networking device. The maximum length of the filename (path and filename) is 100 characters, and the path can point to flash memory on the networking device or to a TFTP or FTP server.

- The eventskeyword turns on event tracing for Cisco Express Forwarding events.

- The interface keyword turns on event tracing for Cisco Express Forwarding interface events.

- The disable keyword turns off event tracing for Cisco Express Forwarding events.

- The enable keyword turns on event tracing for Cisco Express Forwarding events if it had been enabled with the monitor event-trace cef privileged EXEC command.

- The size number keyword and argument pair sets the number of messages that can be written to memory for a single instance of a trace. Range: 1 to 65536.

Note:
Some Cisco IOS software subsystem components set the size by default. To display the size parameter, use the show monitor event-trace cef events parameters command.

- The stacktrace keyword enables the stack trace at tracepoints.

- The depth argument specifies the depth of the stack trace stored. Range: 1 to 16.

Step 4

exit

Example:

Router(config)# exit

Exits to privileged EXEC mode.

Step 5

monitor event-trace cef {dump [merged pretty | pretty] | {events | interface | ipv4 | ipv6} {clear | continuous [cancel] | disable | dump [pretty] | enable | one-shot}}

Example:

Router# monitor event-trace cef events dump pretty

Monitors and controls the event trace function for Cisco Express Forwarding.

- The dump keyword writes the event trace results to the file configured with the monitor event-trace cefglobal configuration command. The trace messages are saved in binary format.

- The merged pretty keywords sort all event trace entries by time and write the entries to a file in ASCII format.

- The pretty keyword saves the event trace message in ASCII format.

- The events keyword monitors Cisco Express Forwarding events.

- The interfacekeyword monitors Cisco Express Forwarding interface events.

- The ipv4keyword monitors Cisco Express Forwarding IPv4 events.

- The ipv6 keyword monitors Cisco Express Forwarding IPv6 events.

- The clear keyword clears existing trace messages for Cisco Express Forwarding from memory on the networking device.

- The continuous keyword continuously displays the latest event trace entries.

- The cancel keyword cancels the continuous display of the latest trace entries.

- The disable keyword turns off Cisco Express Forwarding event tracing.

- The enable keyword turns on Cisco Express Forwarding event tracing.

- The one-shot keyword Clears any existing trace information from memory, starts event tracing again, and disables the trace when the size of the trace message file configured in the global configuration command is exceeded.

Step 6

disable

Example:

Router# disable

Exits to user EXEC mode.

Customizing CEF Event Tracing for IPv4 Events

Perform the following task to customize Cisco Express Forwarding event tracing for Cisco Express Forwarding IPv4 events. Use event tracing to monitor Cisco Express Forwarding IPv4 events as they occur and to help resolve any issues with Cisco Express Forwarding and related IPv4 events.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    monitor event-trace cef ipv4 {disable | distribution |dump-file dump-file-name| enable | match {global | ip-address mask} | size number | stacktrace [depth] | vrf vrf-name [distribution | match {global | ip-address mask}]}

4.    exit

5.    monitor event-trace cef ipv4 {clear | continuous [cancel] | disable | dump [pretty] | enable | one-shot}

6.    disable

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

monitor event-trace cef ipv4 {disable | distribution |dump-file dump-file-name| enable | match {global | ip-address mask} | size number | stacktrace [depth] | vrf vrf-name [distribution | match {global | ip-address mask}]}

Example:

Router(config)# monitor event-trace cef ipv4 size 10000

Configures event-tracing for Cisco Express Forwarding IPv4 events.

- The disable keyword turns off event tracing for Cisco Express Forwarding IPv4 events.

- The distribution keyword logs events related to the distribution of Cisco Express Forwarding Forwarding Information Base (FIB) tables to the line cards

- The dump-file dump-file-name keyword and argument pair specify the file to which event trace messages are written from memory on the networking device. The maximum length of the filename (path and filename) is 100 characters, and the path can point to flash memory on the networking device or to a TFTP or FTP server.

- The enable keyword turns on event tracing for Cisco Express Forwarding IPv4 events if it had been enabled with the monitor event-trace cef privileged EXEC command.

- The matchkeyword turns on event tracing for Cisco Express Forwarding IPv4 events that matches global events or events that match a specific network address

- The globalkeyword specifies global events.

- The ip-address maskargumentsspecify an IP address in A.B.C.D format and a subnet mask in A.B.C.D format.

- The size number keyword and argument pair sets the number of messages that can be written to memory for a single instance of a trace. Range: 1 to 65536.

Note:
Some Cisco IOS software subsystem components set the size by default. To display the size parameter, use the show monitor event-trace cef ipv4 parameters command.

- The stacktrace keyword enables the stack trace at tracepoints.

- The depth argument specifies the depth of the stack trace stored. Range: 1 to 16.

- The vrf vrf-name keyword and argument pair turns on event tracing for a Cisco Express Forwarding IPv4 VRF table. The vrf-name argument specifies the name of the VRF

Step 4

exit

Example:

Router(config)# exit

Exits to privileged EXEC mode.

Step 5

monitor event-trace cef ipv4 {clear | continuous [cancel] | disable | dump [pretty] | enable | one-shot}

Example:

Router# monitor event-trace cef ipv4 continuous

Monitors and controls the event trace function for Cisco Express Forwarding IPv4 events.

- The clear keyword clears existing trace messages for Cisco Express Forwarding from memory on the networking device.

- The continuous keyword continuously displays the latest event trace entries.

- The cancel keyword cancels the continuous display of the latest trace entries.

- The disable keyword turns off Cisco Express Forwarding event tracing.

- The dump keyword writes the event trace results to the file configured with the global configuration monitor event-trace cef command. The trace messages are saved in binary format.

- The pretty keyword saves the event trace message in ASCII format.

- The enable keyword turns on Cisco Express Forwarding event tracing.

- The one-shot keyword clears any existing trace information from memory, starts event tracing again, and disables the trace when the size of the trace message file configured in the global configuration command is exceeded.

Step 6

disable

Example:

Router# disable

Exits to user EXEC mode.

Customizing CEF Event Tracing for IPv6 Events

Perform the following task to customize Cisco Express Forwarding event tracing for Cisco Express Forwarding IPv6 events.Use event tracing to monitor Cisco Express Forwarding IPv6 events as they occur and to help resolve any issues with Cisco Express Forwarding and related IPv6 events.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    monitor event-trace cef ipv4 {disable | distribution | dump-file dump-file-name| enable | match {global | ipv6-address/n} | size number | stacktrace [depth] | vrf vrf-name [distribution | match {global | ipv6-address/n}]}

4.    exit

5.    monitor event-trace cef ipv6 {clear | continuous [cancel] | disable | dump [pretty] | enable | one-shot}}

6.    disable

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

monitor event-trace cef ipv4 {disable | distribution | dump-file dump-file-name| enable | match {global | ipv6-address/n} | size number | stacktrace [depth] | vrf vrf-name [distribution | match {global | ipv6-address/n}]}

Example:

Router(config)# monitor event-trace cef ipv6 match global

Configures event-tracing for Cisco Express Forwarding IPv6 events.

- The disable keyword turns off event tracing for Cisco Express Forwarding IPv6 events.

- The distribution keyword logs events related to the distribution of Cisco Express Forwarding FIB tables to the line cards.

- The dump-file dump-file-name keyword and argument pair specify the file to which event trace messages are written from memory on the networking device. The maximum length of the filename (path and filename) is 100 characters, and the path can point to flash memory on the networking device or to a TFTP or FTP server.

- The enable keyword turns on event tracing for Cisco Express Forwarding IPv6 events if it had been enabled with the monitor event-trace cef privileged EXEC command.

- The matchkeyword turns on event tracing for Cisco Express Forwarding IPv6 events that matches global events or events that match a specific network address.

- The globalkeyword specifies global events.

- The ipv6-address / nargument specifies an IPv6 address. This address must be in the form documented in RFC 2373: the address is specified in hexadecimals using 16-bit values between colons. The slash followed by a number (/ n) indicates the number of bits that do not change. Range: 0 to 128

- The size number keyword and argument pair sets the number of messages that can be written to memory for a single instance of a trace. Range: 1 to 65536.

Note:
Some Cisco IOS software subsystem components set the size by default. To display the size parameter, use the show monitor event-trace cef ipv6 parameters command.

- The stacktrace keyword enables the stack trace at tracepoints.

- The depth argument specifies the depth of the stack trace stored. Range: 1 to 16.

- The vrf vrf-name keyword and argument pair turns on event tracing for a Cisco Express Forwarding IPv6 VRF table. The vrf-name argument specifies the name of the VRF

Step 4

exit

Example:

Router(config)# exit

Exits to privileged EXEC mode.

Step 5

monitor event-trace cef ipv6 {clear | continuous [cancel] | disable | dump [pretty] | enable | one-shot}}

Example:

Router# monitor event-trace cef ipv6 one-shot

Monitors and controls the event trace function for Cisco Express Forwarding IPv6 events.

- The clear keyword clears existing trace messages for Cisco Express Forwarding from memory on the networking device.

- The continuous keyword continuously displays the latest event trace entries.

- The cancel keyword cancels the continuous display of the latest trace entries.

- The disable keyword turns off Cisco Express Forwarding event tracing.

- The dump keyword writes the event trace results to the file configured with the global configuration monitor event-trace cef command. The trace messages are saved in binary format.

- The pretty keyword saves the event trace message in ASCII format.

- The enable keyword turns on Cisco Express Forwarding event tracing.

- The one-shot keyword Clears any existing trace information from memory, starts event tracing again, and disables the trace when the size of the trace message file configured in the global configuration command is exceeded.

Step 6

disable

Example:

Router# disable

Exits to privileged EXEC mode.

Displaying CEF Event Trace Information

Perform the following task to display Cisco Express Forwarding event trace information.

SUMMARY STEPS

1.    enable

2.    monitor event-trace cef events clear

3.    debug ip cef table

4.    show monitor events-trace cef all

5.    show monitor event-trace cef latest

6.    show monitor event-trace cef events all

7.    show monitor event-trace cef interface latest

8.    show monitor event-trace cef ipv4 all

9.    show monitor event-trace cef ipv6 parameters

10.    disable

DETAILED STEPS

Step 1

enable

Use this command to enable privileged EXEC mode. Enter your password if prompted. For example:

Example:

Router> enable
Router#

Step 2

monitor event-trace cef events clear

Use this command to clear the Cisco Express Forwarding event trace buffer. For example:

Router# monitor event-trace cef clear

Example:

Step 3

debug ip cef table

Use this command to display events that affect entries in the Cisco Express Forwarding tables. For example:

Example:

Router# debug ip cef table
01:25:46:CEF-Table:Event up, 10.1.1.1/32 (rdbs:1, flags:1000000)
01:25:46:CEF-IP:Checking dependencies of 0.0.0.0/0
01:25:47:CEF-Table:attempting to resolve 10.1.1.1/32
01:25:47:CEF-IP:resolved 10.1.1.1/32 via 10.9.104.1 to 10.9.104.1 Ethernet2/0/0
01:26:02:CEF-Table:Event up, default, 0.0.0.0/0 (rdbs:1, flags:400001)
01:26:02:CEF-IP:Prefix exists - no-op change

Step 4

show monitor events-trace cef all

Use this command to display event trace messages for Cisco Express Forwarding. For example:

Example:

Router# show monitor event-trace cef all
cef_events:
*Jul 22 20:14:58.999: SubSys  ipv4fib_ios_def_cap init
*Jul 22 20:14:58.999: SubSys  ipv6fib_ios_def_cap init
*Jul 22 20:14:58.999: Inst    unknown -> RP
*Jul 22 20:14:58.999: SubSys  fib_ios_chain init
*Jul 22 20:14:59.075: SubSys  fib init
*Jul 22 20:14:59.075: SubSys  ipv4fib init
*Jul 22 20:14:59.075: SubSys  fib_ios init
*Jul 22 20:14:59.075: SubSys  fib_ios_if init
*Jul 22 20:14:59.075: SubSys  ipv4fib_ios init
*Jul 22 20:14:59.075: Flag    Common CEF enabled set to yes
*Jul 22 20:14:59.075: Flag    IPv4 CEF enabled set to yes
*Jul 22 20:14:59.075: Flag    IPv4 CEF switching enabled set to yes
*Jul 22 20:14:59.075: GState  CEF enabled
*Jul 22 20:14:59.075: SubSys  ipv6fib_ios init
*Jul 22 20:14:59.075: SubSys  ipv4fib_util init
*Jul 22 20:14:59.075: SubSys  ipv4fib_les init
*Jul 22 20:15:02.907: Process Background created
*Jul 22 20:15:02.907: Flag    IPv4 CEF running set to yes
*Jul 22 20:15:02.907: Process Background event loop enter
*Jul 22 20:15:02.927: Flag    IPv4 CEF switching running set to yes

cef_interface:
*Jul 22 20:14:58.999: Et0/0        (hw  3) SWvecLES <unknown> (0x01096A3C)
*Jul 22 20:14:58.999: Et0/1        (hw  4) SWvecLES <unknown> (0x01096A3C)
*Jul 22 20:14:58.999: Et0/2        (hw  5) SWvecLES <unknown> (0x01096A3C)
*Jul 22 20:14:58.999: Et0/3        (hw  6) SWvecLES <unknown> (0x01096A3C)
*Jul 22 20:14:58.999: Et1/0        (hw  7) SWvecLES <unknown> (0x01096A3C)
*Jul 22 20:14:58.999: Et1/1        (hw  8) SWvecLES <unknown> (0x01096A3C)
*Jul 22 20:14:58.999: Et1/2        (hw  9) SWvecLES <unknown> (0x01096A3C)
*Jul 22 20:14:58.999: Et1/3        (hw 10) SWvecLES <unknown> (0x01096A3C)
*Jul 22 20:14:58.999: Se2/0        (hw 11) SWvecLES <unknown> (0x01096A3C)
*Jul 22 20:14:58.999: Se2/1        (hw 12) SWvecLES <unknown> (0x01096A3C)
.
.
.

The output is in table format where the first column contains a time stamp, the second column lists the type of event, and the third column lists the detail for the event.

Step 5

show monitor event-trace cef latest

Use this command to display only the event trace message that have been sent since the last instance of the show monitor event-trace cef command. For example:

Example:

Router# show monitor event-trace cef latest
cef_events:
cef_interface:
*Jul 22 20:14:59.075: Se3/0        (sw 15) FlagCha  0x60C1 add puntLC
*Jul 22 20:14:59.075: <empty>      (hw 16) State    down -> up
*Jul 22 20:14:59.075: <empty>      (hw 16) Create   new
*Jul 22 20:14:59.075: Se3/1        (hw 16) NameSet
*Jul 22 20:14:59.075: Se3/1        (hw 16) HWIDBLnk Serial3/1(16)
*Jul 22 20:14:59.075: Se3/1        (hw 16) RCFlags  None -> Fast
*Jul 22 20:14:59.075: <empty>      (sw 16) VRFLink  IPv4:id0 - success
*Jul 22 20:14:59.075: <empty>      (sw 16) State    deleted -> down
*Jul 22 20:14:59.075: <empty>      (sw 16) Create   new
*Jul 22 20:14:59.075: Se3/1        (sw 16) NameSet
*Jul 22 20:14:59.075: Se3/1        (sw 16) FIBHWLnk Serial3/1(16)
*Jul 22 20:14:59.075: Se3/1        (sw 16) SWIDBLnk Serial3/1(16)
*Jul 22 20:14:59.075: Se3/1        (sw 16) FlagCha  0x6001 add p2p|input|first
*Jul 22 20:14:59.075: Se3/1        (sw 16) FlagCha  0x6041 add auto_adj
*Jul 22 20:14:59.075: Se3/1        (sw 16) Impared  lc rea Queueing configuration
*Jul 22 20:14:59.075: Se3/1        (sw 16) FlagCha  0x60C1 add puntLC
*Jul 22 20:14:59.075: <empty>      (hw 17) State    down -> up
*Jul 22 20:14:59.075: <empty>      (hw 17) Create   new
*Jul 22 20:14:59.075: Se3/2        (hw 17) NameSet

Step 6

show monitor event-trace cef events all

Use this command to display information about Cisco Express Forwarding events. For example:

Example:

Router# show monitor event-trace cef events all
*Jul 13 17:38:27.999: SubSys  ipv4fib_ios_def_cap init
*Jul 13 17:38:27.999: SubSys  ipv6fib_ios_def_cap init
*Jul 13 17:38:27.999: Inst    unknown -> RP
*Jul 13 17:38:27.999: SubSys  fib_ios_chain init
*Jul 13 17:38:28.199: SubSys  fib init
*Jul 13 17:38:28.199: SubSys  ipv4fib init
*Jul 13 17:38:28.199: SubSys  fib_ios init
*Jul 13 17:38:28.199: SubSys  fib_ios_if init
*Jul 13 17:38:28.199: SubSys  ipv4fib_ios init
*Jul 13 17:38:28.199: Flag    Common CEF enabled set to yes
*Jul 13 17:38:28.199: Flag    IPv4 CEF enabled set to yes
*Jul 13 17:38:28.199: Flag    IPv4 CEF switching enabled set to yes
*Jul 13 17:38:28.199: GState  CEF enabled
*Jul 13 17:38:28.199: SubSys  ipv6fib_ios init
*Jul 13 17:38:28.199: SubSys  ipv4fib_util init
*Jul 13 17:38:28.199: SubSys  ipv4fib_les init
*Jul 13 17:38:34.059: Process Background created
*Jul 13 17:38:34.059: Flag    IPv4 CEF running set to yes
*Jul 13 17:38:34.059: Process Background event loop enter
*Jul 13 17:38:34.079: Flag    IPv4 CEF switching running set to yes

The output is in table format where the first column contains a time stamp, the second column lists the type of event, and the third column lists the detail for the event.

For example, the Subsys event type is related to the initialization of a subset of Cisco Express Forwarding functionality. The "ipv4fib_ios_def_cap init" entry is the initialization of IPv4 Cisco Express Forwarding default capabilities.

Step 7

show monitor event-trace cef interface latest

Use this command to display only the event trace messages generated since the last show monitor event-trace cef interfacecommand was entered. For example:

Example:

Router# show monitor event-trace cef interface latest
*Jul 22 20:14:58.999: Et0/0        (hw  3) SWvecLES <unknown> (0x01096A3C)
*Jul 22 20:14:58.999: Et0/1        (hw  4) SWvecLES <unknown> (0x01096A3C)
*Jul 22 20:14:58.999: Et0/2        (hw  5) SWvecLES <unknown> (0x01096A3C)
*Jul 22 20:14:58.999: Et0/3        (hw  6) SWvecLES <unknown> (0x01096A3C)
.
.
.
*Jul 22 20:14:59.075: <empty>      (hw  3) State    down -> up
*Jul 22 20:14:59.075: <empty>      (hw  3) Create   new
*Jul 22 20:14:59.075: Et0/0        (hw  3) NameSet
*Jul 22 20:14:59.075: Et0/0        (hw  3) HWIDBLnk Ethernet0/0(3)
*Jul 22 20:14:59.075: Et0/0        (hw  3) RCFlags  None -> Fast
*Jul 22 20:14:59.075: <empty>      (sw  3) VRFLink  IPv4:id0 - success
*Jul 22 20:14:59.075: <empty>      (sw  3) State    deleted -> down
*Jul 22 20:14:59.075: <empty>      (sw  3) Create   new
*Jul 22 20:14:59.075: Et0/0        (sw  3) NameSet
*Jul 22 20:14:59.075: Et0/0        (sw  3) FIBHWLnk Ethernet0/0(3)
*Jul 22 20:14:59.075: Et0/0        (sw  3) SWIDBLnk Ethernet0/0(3)
*Jul 22 20:14:59.075: Et0/0        (sw  3) FlagCha  0x6000 add input|first
*Jul 22 20:14:59.075: Et0/0        (sw  3) State    down -> up
*Jul 22 20:14:59.075: <empty>      (hw  4) State    down -> up
*Jul 22 20:14:59.075: <empty>      (hw  4) Create   new
*Jul 22 20:14:59.075: Et0/1        (hw  4) NameSet
*Jul 22 20:14:59.075: Et0/1        (hw  4) HWIDBLnk Ethernet0/1(4)
*Jul 22 20:14:59.075: Et0/1        (hw  4) RCFlags  None -> Fast
*Jul 22 20:14:59.075: <empty>      (sw  4) VRFLink  IPv4:id0 - success
*Jul 22 20:14:59.075: <empty>      (sw  4) State    deleted -> down
*Jul 22 20:14:59.075: <empty>      (sw  4) Create   new
*Jul 22 20:14:59.075: Et0/1        (sw  4) NameSet
*Jul 22 20:14:59.075: Et0/1        (sw  4) FIBHWLnk Ethernet0/1(4)
*Jul 22 20:14:59.075: Et0/1        (sw  4) SWIDBLnk Ethernet0/1(4)
*Jul 22 20:14:59.075: Et0/1        (sw  4) FlagCha  0x6000 add input|first
*Jul 22 20:14:59.075: Et0/1        (sw  4) State    down -> up
.
.
.

Step 8

show monitor event-trace cef ipv4 all

Use this command to display information about Cisco Express Forwarding IPv4 events. For example:

Example:

Router# show monitor event-trace cef ipv4 all
*Jul 22 20:14:59.075:  [Default] *.*.*.*/*             Allocated FIB table
[OK]
*Jul 22 20:14:59.075:  [Default] *.*.*.*/*'00          Add source Default table
[OK]
*Jul 22 20:14:59.075:  [Default] 0.0.0.0/0'00          FIB add src DRH (ins)
[OK]
*Jul 22 20:14:59.075:  [Default] *.*.*.*/*'00          New FIB table
[OK]
*Jul 22 20:15:02.927:  [Default] *.*.*.*/*'00          FIB refresh start
[OK]
.
.
.

Step 9

show monitor event-trace cef ipv6 parameters

Use this commands to display parameters configured for Cisco Express Forwarding IPv6 events. For example:

Example:

Router# show monitor event-trace cef ipv6 parameters
Trace has 1000 entries
Stacktrace is disabled by default
Matching all events

Step 10

disable

Use this command to exit to user EXEC mode. For example:

Example:

Router# disable
Router>

Configuration Examples for the Display of CEF Event Trace Messages

- Example Customizing CEF Event Tracing

- Example Customizing CEF Event Tracing for IPv4 Events

- Example Customizing CEF Event Tracing for IPv6 Events

Example Customizing CEF Event Tracing

The following example shows how to enable event tracing for Cisco Express Forwarding and configure the buffer size to 2500 messages. The trace messages file is set to cef-dump in slot0 (flash memory).

configure terminal
!
monitor event-trace cef events enable
monitor event-trace cef dump-file slot0:cef-dump
monitor event-trace cef events size 2500
exit
The following example shows what happens when you try to enable event tracing for Cisco Express Forwarding events when it is already enabled:
configure terminal
!
monitor event-trace cef events enable
00:04:33: %EVENT_TRACE-6-ENABLE: Trace already enabled.

The following example shows the privileged EXEC commands that stop event tracing, clear the current contents of memory, and reenable the trace function for Cisco Express Forwarding events. This example assumes that the tracing function is configured and enabled on the networking device.

enable
!
monitor event-trace cef events disable
monitor event-trace cef events clear
monitor event-trace cef events enable
disable

Example Customizing CEF Event Tracing for IPv4 Events

The following example shows how to enable event tracing for Cisco Express Forwarding IPv4 events and configure the buffer size to 5000 messages:

configure terminal
!
monitor event-trace cef ipv4 enable
monitor event-trace cef ipv4 size 5000
exit
The following example shows how to enable event tracing for events that match Cisco Express Forwarding IPv4 VRF vpn1:
configure terminal
!
monitor event-trace cef ipv4 enable
monitor event-trace cef ipv4 vrf vpn1
exit

The following example shows the privileged EXEC commands to configure the continuous display of the latest Cisco Express Forwarding event trace entries for IPv4 events:

enable
!
monitor event-trace cef ipv4 continuous
disable

The following example shows how to stop the continuous display of the latest trace entries:

enable
!
monitor event-trace cef ipv4 continuous cancel
disable

Example Customizing CEF Event Tracing for IPv6 Events

The following example shows how to enable event tracing for Cisco Express Forwarding IPv6 events and configure the buffer size to 10000:

configure terminal
!
monitor event-trace cef ipv6 enable
monitor event-trace cef ipv6 size 10000
exit

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

Cisco Express Forwarding commands

Cisco IOS IP Switching Command Reference

Overview of the Cisco Express Forwarding feature

Cisco Express Forwarding Overview

Tasks for verifying basic Cisco Express Forwarding and distributed Cisco Express Forwarding operation

Configuring Basic Cisco Express Forwarding for Improved Performance, Scalability, and Resiliency in Dynamic Networks

Tasks for enabling or disabling Cisco Express Forwarding or distributed Cisco Express Forwarding

Enabling or Disabling Cisco Express Forwarding or Distributed Cisco Express Forwarding to Customize Switching and Forwarding for Dynamic Networks

Tasks for configuring load-balancing schemes for Cisco Express Forwarding

Configuring a Load-Balancing Scheme for Cisco Express Forwarding Traffic

Tasks for configuring Cisco Express Forwarding consistency checkers

Configuring Cisco Express Forwarding Consistency Checkers for Route Processors and Line Cards

Tasks for configuring epochs for Cisco Express Forwarding tables

Configuring Epochs to Clear and Rebuild Cisco Express Forwarding and Adjacency Tables

Tasks for configuring and verifying Cisco Express Forwarding network accounting

Configuring Cisco Express Forwarding Network Accounting

Tasks for customizing the display of recorded Cisco Express Forwarding events in Cisco IOS releases prior to Cisco IOS Releases 12.2(25)S, 12.2(33)SB, 12.2(33)SRA, 12.2(33)SXH, and 12.4(20)T

Customizing the Display of Recorded Cisco Express Forwarding Events

Causes of common Cisco Express Forwarding-related error messages on platforms running distributed Cisco Express Forwarding switching (Cisco 7500 series routers and Cisco 12000 series Internet routers) and how to troubleshoot them

Troubleshooting Cisco Express Forwarding-Related Error Messages

Standards

Standard

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

--

MIBs

MIB

MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

Click Here

RFCs

RFC

Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

--

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

Click Here

Feature Information for the Display of CEF Event Trace Messages

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.

Feature Information for Configuring the Display of Cisco Express Forwarding Event Trace Messages

Feature Name

Releases

Feature Configuration Information

This table is intentionally left blank because no features were introduced or modified in Cisco IOS Release 12.2(1) or later. This table will be updated when feature information is added to this module.

--

--

Glossary

adjacency --A relationship formed between selected neighboring routers and end nodes for the purpose of exchanging routing information. Adjacency is based upon the use of a common media segment by the routers and nodes involved.

Cisco Express Forwarding --A Layer 3 switching technology. Cisco Express Forwarding can also refer to central Cisco Express Forwarding mode, one of two modes of Cisco Express Forwarding operation. Cisco Express Forwarding enables a Route Processor to perform express forwarding. Distributed Cisco Express Forwarding is the other mode of Cisco Express Forwarding operation.

distributed Cisco Express Forwardin g--A mode of Cisco Express Forwarding operation in which line cards (such as Versatile Interface Processor (VIP) line cards) maintain identical copies of the forwarding information base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters; this relieves the Route Switch Processor of involvement in the switching operation.

FIB --forwarding information base. A component of Cisco Express Forwarding that is conceptually similar to a routing table or information base. The router uses the FIB lookup table to make destination-based switching decisions during Cisco Express Forwarding operation. The router maintains a mirror image of the forwarding information in an IP routing table.

line card --A general term for an interface processor that can be used in various Cisco products. For example, a Versatile Interface Processor (VIP) is a line card for the Cisco 7500 series router.

prefix --The network address portion of an IP address. A prefix is specified by a network and mask and is generally represented in the format network/mask. The mask indicates which bits are the network bits. For example, 1.0.0.0/16 means that the first 16 bits of the IP address are masked, making them the network bits. The remaining bits are the host bits. In this example, the network number is 10.0.

VPN --Virtual Private Network. The result of a router configuration that enables IP traffic to use tunneling to travel securely over a public TCP/IP network.

VRF --A Virtual Private Network (VPN) routing/forwarding instance. A VRF consists of an IP routing table, a derived forwarding table, a set of interfaces that use the forwarding table, and a set of rules and routing protocols that determine what goes into the forwarding table. In general, a VRF includes the routing information that defines a customer VPN site that is attached to a PE router.

Chapter 10. SNMP CEF-MIB Support

The Cisco Express Forwarding--SNMP CEF-MIB Support feature introduces the CISCO-CEF-MIB, which allows management applications through the use of the Simple Network Management Protocol (SNMP) to configure and monitor Cisco Express Forwarding operational data and to provide notification when Cisco Express Forwarding encounters specific configured events. This module describes how to use the CISCO-CEF-MIB to manage and monitor objects related to Cisco Express Forwarding operation.

Cisco Express Forwarding is an advanced Layer 3 IP switching technology. It optimizes network performance and scalability for all kinds of networks: those that carry small amounts of traffic and those that carry large amounts of traffic in complex patterns, such as the Internet and networks characterized by intensive web-based applications or interactive sessions.

- Finding Feature Information

- Prerequisites for SNMP CEF-MIB Support

- Information About SNMP CEF-MIB Support

- How to Configure SNMP CEF-MIB Support

- Configuration Examples for SNMP CEF-MIB Support

- Additional References

- Feature Information for SNMP CEF-MIB Support

- Glossary

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to Click Here . An account on Cisco.com is not required.

Prerequisites for SNMP CEF-MIB Support

- Cisco Express Forwarding or distributed Cisco Express Forwarding must be configured on your system.

- The Cisco Express Forwarding infrastructure introduced in Cisco IOS Release12.2(25)S must be included in the image on your system.

- The router on which the Cisco Express Forwarding--SNMP CEF-MIB Support features is to be used must be configured for SNMP access. See the Configuring the Router to Use SNMP of this document for more information.

Information About SNMP CEF-MIB Support

- CEF Functional Overview

- Benefits of CISCO-CEF-MIB

- Information Managed by the CISCO-CEF-MIB

- CISCO-CEF-MIB Object Groups

- CISCO-CEF-MIB Tables

- Operations Available Through the CISCO-CEF-MIB

- CISCO-CEF-MIB Notifications

CEF Functional Overview

Cisco Express Forwarding is an advanced Layer 3 IP switching technology. It uses a Forwarding Information Base (FIB) to make IP destination prefix-based switching decisions. The FIB is conceptually similar to a routing table or information base. It maintains the forwarding information contained in the IP routing table. When routing or topology changes occur in the network, the IP routing table is updated, and those changes are propagated to the FIB. The FIB maintains next-hop address information based on the information in the IP routing table. The two main components of Cisco Express Forwarding operation are the FIB and adjacency tables.

Cisco Express Forwarding uses adjacency tables to prepend Layer 2 addressing information. An adjacency table maintains Layer 2 next-hop addresses for all FIB entries. Nodes in the network are said to be adjacent if they can reach each other with a single hop across a link layer. Cisco Express Forwarding discovers and solves adjacencies and populates the adjacency tables.

Note

The CISCO-CEF-MIB prefix database and its related database can be very large. Therefore, executing a command that displays the prefix table could take a considerable amount of time.

Benefits of CISCO-CEF-MIB

Command-line interface (CLI) show commands are available to obtain Cisco Express Forwarding operational information. Managing Cisco Express Forwarding using the CLI can be a time-consuming task. The increasing capacity of Cisco routers makes parsing the show commands output to obtain the needed Cisco Express Forwarding operational parameters more and more difficult.

In Cisco IOS Release 12.2(31)SB and later releases, the CISCO-CEF-MIB allows you to manage and monitor the Cisco Express Forwarding operation using SNMP. In addition, you can configure SNMP to notify you if Cisco Express Forwarding encounters errors.

The CISCO-CEF-MIB introduced with the Cisco Express Forwarding--SNMP CEF-MIB Support feature gives you real-time access to operational information stored in the FIB and adjacency tables, switching statistics, and information on resource failures. The feature enables you to configure parameters related to Cisco Express Forwarding features by utilizing a MIB implementation based on SNMP. This information is accessed using get and set commands entered on the network management system (NMS) workstation or host system for which SNMP has been implemented. The NMS workstation is also known as the SNMP manager.

Cisco Express Forwarding is available in all Cisco routers. However, CISCO-CEF-MIB support of Cisco Express Forwarding management is dependent on the infrastructure introduced in Cisco IOS Release 12.2(22)S.

The implementation of the CISCO-CEF-MIB in Cisco IOS Release 12.2(31)SB2, Cisco IOS Release 12.2(33)SRC,and Cisco IOS Release 12.2(33)SB manages Cisco Express Forwarding instances running on the Route Processor (RP). Information about Cisco Express Forwarding running on the line cards is available to the RP in reference to Cisco Express Forwarding peers only.

The CISCO-CEF-MIB supports configuration and monitoring for both IP versions, IP Version 4 (IPv4) and IP Version 6 (IPv6).

Information Managed by the CISCO-CEF-MIB

SNMP has historically been used to collect network information. SNMP permits retrieval of critical information from network elements such as routers, switches, and workstations.

The CISCO-CEF-MIB provides managed objects that enable a network administrator to monitor the following:

- Cisco Express Forwarding administrative and operational states as displayed in the output of the show ip cef summary command

- Notifications for Cisco Express Forwarding events: Cisco Express Forwarding state changes, Cisco Express Forwarding failures (with a predefined reason), and Route Processor (RP) and line card inconsistencies

- Parameters related to Cisco Express Forwarding for the associated interface as displayed by the show cef interface command

- Line card Cisco Express Forwarding states and line card Cisco Express Forwarding FIB states in the Linecard table as displayed by the show cef linecardcommand

- Cisco Express Forwarding statistics: switching statistics, punt counters and punt-to-host counters as displayed by the show ip cef switching statscommand, and per-prefix counters and nonrecursive counters

- IPv4 and IPv6 notification, when Cisco Express Forwarding is switched between disable and enable and between Cisco Express Forwarding and distributed Cisco Express Forwarding

The SNMP CISCO-CEF-MIB provides managed objects that enable a network administrator to configure the following:

- Cisco Express Forwarding and distributed Cisco Express Forwarding administration status

- Cisco Express Forwarding accounting-related parameters

- Cisco Express Forwarding load sharing-related parameters

- Traffic-related configuration parameters

CISCO-CEF-MIB Object Groups

The SNMP CISCO-CEF-MIB allows the configuration and management of objects related to Cisco Express Forwarding. The MIB contains the following object groups:

- CEF FIB group

- CEF Adjacency group

- CEF Forwarding Element group

- CEF Cfg group

- CEF Interface group

- CEF Peer group

- CEF Consistency (CC) group

- CEF State Group

- CEF Notification Control group

In the CISCO-CEF-MIB, configuration objects are defined as read-write, and the other objects are defined as read only.

The CISCO-CEF-MIB contains tables related to the Cisco Express Forwarding object groups. These tables provide information about prefixes, forwarding paths, adjacencies, output chain elements (OCEs), prefix-based statistics, information about Cisco Express Forwarding configuration, consistency checkers, switching statistics, and managed objects specific to line card-specific.

The CISCO-CEF-MIB also defines Cisco Express Forwarding notifications that you can enable or disable through the MIB or CLI commands.

The index for most tables in the CISCO-CEF-MIB is entPhysicalIndex.

CISCO-CEF-MIB Tables

- The CEF FIB Summary table (cefFIBSummaryTable) contains the number of forwarding prefixes for both IPv4 and IPv6 protocols. It is a summary of the CEF Forwarding table.

- The CEF Forwarding table (cefPrefixTable) lists all the prefixes and related counters. It also contains a pointer to the CEF Forwarding Element Selection table.

- The CEF Longest Match Prefix table (cefLMPrefixTable) returns the longest prefix match for the given destination address. An optional cefLMPrefixSpinLock object is provided to reduce conflict in instances when more than one application acts on the CEF Longest Match Prefix table.

- The CEF Path table (cefPathTable) lists all the Cisco Express Forwarding paths.

- The CEF Adjacency Summary table (cefAdJSummaryTable) contains the total number of complete, incomplete, fixup, and redirect adjacencies for all link types.

- The CEF Adjacency table (cefAdjTable) lists all the adjacencies. It contains the adjacency source, encapsulation string, fixup, and Layer 3 maximum transmission unit (MTU) associated with the adjacency entry. It contains a pointer to the forwarding element selection table (if the adjacency is a MID chain adjacency).

- The CEF Forwarding Element Selection table (cefFESelectionTable) represents the OCE chains in flattened format. This table shows only the labels, table ID, and adjacency traversed in the OCE chain. It also contains the weight associated with each OCE chain.

- CEF Cfg table (cefCfgTable) contains all the global configuration parameters related to Cisco Express Forwarding: administration and operational status, accounting-related configuration parameters, load-sharing algorithms and IDs, and traffic statistics parameters.

- CEF Resource table (cefResourceTable) contains information about resources for Cisco Express Forwarding: the memory status of the process memory pool and reasons for the Cisco Express Forwarding resource failure notifications.

- CEF Interface table (cefIntTable) contains the interface-specific Cisco Express Forwarding parameters: interface switching state, interface load sharing (per packet and per destination), and interface nonrecursive routing (internal and external).

- CEF Peer table or Linecard table (cefPeerTable) contains Cisco Express Forwarding information related to peers on a managed line card: line card operational state and the number of times the line card session resets.

- CEF Peer FIB table (cefPeerFIBTable) contains information about the operational state of the Forwarding Information Bases (FIBs) on each line card.

- The CEF Prefix Length Statistics table (cefStatsPrefixTable) maintains prefix length-based statistics.

- CEF Switching Statistics table (cefSwitchingStatsTable) contains the switching statistics for each switching path: drop counters, punt counters, and punt-to-host counters.

- CEF IP Prefix Consistency Checker Global group (cefCCGlobalTable) contains all global configuration parameters for the consistency checkers: auto repair, enable and disable, delay, and hold down; enable or disable the passive consistency checkers; enable or disable the error messages for consistency detection; and the mechanism to activate the full scan consistency checkers. This table also displays the state of full scan consistency checkers.

- CEF Consistency Checker Type table (cefCCTypeTable) contains the consistency checker type specific parameters: frequency and count of scan for passive scanners and the queries sent, ignored, checked, and iterated.

- CEF Inconsistency Record table (cefInconsistencyRecordTable) contains the detected inconsistency records: prefix address and length, table ID, consistency checker type, slot ID, and the reason for the inconsistency (missing or checksum error).

See theOperations Available Through the CISCO-CEF-MIB for information about the specific objects available through the CISCO-CEF-MIB tables.

The figure below shows the contents of the CISCO-CEF-MIB main tables and the relationships of the tables to one another.

CISCO-CEF-MIB Main Tables, Table Contents, and Relationships

Operations Available Through the CISCO-CEF-MIB

You can use SNMP getand setcommands to configure and monitor Cisco Express Forwarding operations that are available through the CISCO-CEF-MIB tables. This section describes the configuration and monitoring operations for each table.

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF FIB Summary table (cefFIBSummaryTable).

CEF FIB Summary Table--Cisco Express Forwarding Operation and Associated MIB Object

Cisco Express Forwarding Operation

Description

Gets the number of forwarding prefixes for IPv4 and IPv6

cefFIBSummaryFwdPrefixes

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Forwarding table (cefPrefixTable).

CEF Forwarding Table--Cisco Express Forwarding Operations and Associated MIB Objects

Cisco Express Forwarding Operation

MIB Object

Gets the forwarding information for the entry

cefPrefixForwardingInfo

Gets the number of packets forwarded by the prefix

cefPrefixPkts

Gets the number of packets forwarded by the prefix in a 64-bit value

cefPrefixHCPkts

Gets the number of bytes forwarded by the prefix

cefPrefixBytes

Gets the number of bytes forwarded by the prefix in a 64-bit value

cefPrefixHCBytes

Gets the number of internal nonrecursive packets forwarded by the prefix

cefPrefixInternalNRPkts

Gets the number of internal nonrecursive packets forwarded by the prefix in a 64-bit value

cefPrefixInternalNRHCPkts

Gets the number of internal nonrecursive bytes forwarded by the prefix

cefPrefixInternalNRBytes

Gets the number of internal nonrecursive bytes forwarded by the prefix in a 64-bit value

cefPrefixInternalNRHCBytes

Gets the number of external nonrecursive packets forwarded by the prefix

cefPrefixExternalNRPkts

Gets the number of external nonrecursive packets forwarded by the prefix in a 64-bit value

cefPrefixExternalNRHCPkts

Gets the number of external nonrecursive bytes forwarded by the prefix

cefPrefixExternalNRBytes

Gets the number of external nonrecursive bytes forwarded by the prefix in 64-bit value

cefPrefixExternalNRHCBytes

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Longest Match Prefix table (cefLMPrefixTable).

CEF Longest Match Prefix Table--Cisco Express Forwarding Operations and Associated MIB Objects

Cisco Express Forwarding Operation

MIB Object

Gets or sets the lock for creation or modification of the longest match prefix entries

cefLMPrefixSpinLock

Gets the state of the destination prefix request

cefLMPrefixState

Gets the network prefix address for the destination prefix request

cefLMPrefixAddr

Gets the network prefix length for the destination prefix request (the same display as the show ip cef exact-route command)

cefLMPrefixLen

Gets the status of a table entry

cefLMPrefixRowStatus

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Path table (cefPathTable).

CEF Path Table--Cisco Express Forwarding Operations and Associated MIB Objects

Cisco Express Forwarding Operation

MIB Object

Gets the type of Cisco Express Forwarding path for a prefix

cefPathType

Gets the interface associated with this Cisco Express Forwarding path

cefPathInterface

Gets the next-hop address for the Cisco Express Forwarding path

cefPathNextHopAddr

Gets the recursive Virtual Private Network (VPN) routing and forwarding (VRF) instance name associated with this path

cefPathRecurseVrfName

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Adjacency Summary table (cefAdjSummaryTable).

CEF Adjacency Summary Table--Cisco Express Forwarding Operations and Associated MIB Objects

Cisco Express Forwarding Operation

MIB Objects

Gets the number of complete adjacencies

cefAdjSummaryComplete

Gets the number of incomplete adjacencies

cefAdjSummaryInComplete

Gets the number of adjacencies for Layer 2 encapsulation

cefAdjSummaryFixup

Gets the number of adjacencies for IP redirect

cefAdjSummaryRedirect

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Adjacency table (cefAdjTable).

CEF Adjacency Table--Cisco Express Forwarding Operations and Associated MIB Objects

Cisco Express Forwarding Operation

MIB Object

Gets the adjacency source

cefAdjSource

Gets the adjacency Layer 2 encapsulation

cefAdjEncap

Gets the adjacency fixup

cefAdjFixup

Gets the Layer 3 maximum transmission unit (MTU) for the adjacency

cefAdjMTU

Gets the forwarding information in cefFESelectionTable

cefAdjForwardingInfo

Gets the number of packets transmitted

cefAdjPkts

Gets the number of packets transmitted in a 64-bit version

cefAdjHCPkts

Gets the number of bytes transmitted

cefAdjBytes

Gets the number of bytes transmitted in a 64-bit version

cefAdjHCBytes

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Forwarding Element Selection table (cefFESelectionTable).

CEF Forwarding Element Selection Table--Cisco Express Forwarding Operations and Associated MIB Objects

Cisco Express Forwarding Operation

MIB Object

Gets any special processing for a forwarding element

cefFESelectionSpecial

Gets the Multiprotocol Label Switching (MPLS) labels for a forwarding element

cefFESelectionLabels

Gets the adjancency type for a forwarding element

cefFESelectionAdjLinkType

Gets the interface for the adjacency for a forwarding element

cefFESelectionAdjInterface

Gets the next-hop address type for the adjacency for a forwarding element

cefFESelectionAdjNextHopAddrType

Gets the next-hop address for the adjacency for a forwarding element

cefFESelectionAdjNextHopAddr

Gets the connection ID for the adjacency for a forwarding element

cefFESelectionAdjConnId

Gets the VRF name for the lookup for a forwarding element

cefFESelectionVrfName

Gets the weighting for load balancing for a forwarding element

cefFESelectionWeight

The table below lists the Cisco Express Forwarding configuration and monitoring operations and associated MIB objects provided by the CEF Cfg table (cefCfgTable).

CEF Cfg Table--Cisco Express Forwarding Operations and Associated MIB Objects

Cisco Express Forwarding Operation

MIB Objects

Enables or disables a Cisco Express Forwarding instance

cefCfgAdminState

Queries a Cisco Express Forwarding operational instance

cefCfgOperState

Enables or disables a distributed Cisco Express Forwarding instance

cefCfgDistributionAdminState

Queries a distributed Cisco Express Forwarding operational instance

cefCfgDistributionOperState

Gets or sets Cisco Express Forwarding network accounting options

cefCfgAccountingMap

- nonRecursive (0)

- perPrefix (1)

- prefixLength (2)

Gets or sets Cisco Express Forwarding load sharing algorithm options

cefCfgLoadSharingAlgorithm

- none (1) - Load sharing is disabled.

- original (2)

- tunnel (3)

- universal (4)

Gets or sets a load sharing ID

cefCfgLoadSharingID

Gets or sets a traffic interval timer for Cisco Express Forwarding traffic statistics

cefCfgTrafficStatsLoadInterval

Gets or sets a frequency timer for the line card to send traffic statistics to the RP

cefCfgTrafficStatsUpdateRate

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Resource table (cefResourceTable).

CEF Resource Table--Cisco Express Forwarding Operations and Associated MIB Objects

Cisco Express Forwarding Operation

MIB Object

Gets the memory status of process memory pool for Cisco Express Forwarding

cefResourceMemoryUsed

Gets the reason for the Cisco Express Forwarding resource failure notification

cefResourceFailureReason

The table below lists the Cisco Express Forwarding configuration and monitoring operations and associated MIB objects provided by the CEF Interface table (cefIntTable).

CEF Interface Table--Cisco Express Forwarding Operations and Associated MIB Objects

Cisco Express Forwarding Operation

MIB Objects

Gets or sets the Cisco Express Forwarding switching state of the interface

cefIntSwitchingState

- cefEnabled (1)

- distCefEnabled (2)

- cefDisabled (3)

Gets or sets the type of Cisco Express Forwarding Load sharing on the interface

cefIntLoadSharing

- perPacket (1)

- perDestination (2)

Gets or sets Cisco Express Forwarding nonrecursive accounting on the interface

cefIntNonrecursiveAccouting

- internal (1)

- external (2)

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Peer table (or Linecard table) (cefPeerTable).

CEF Peer Table--Cisco Express Forwarding Operations and Associated MIB Objects

Cisco Express Forwarding Operation

MIB Objects

Gets the Cisco Express Forwarding operational instance of the peer entity

cefPeerOperState

Gets how many times the session with the Peer resets

cefPeerNumberOfResets

The table below lists the Cisco Express Forwarding monitoring operation and associated MIB object provided by the CEF Peer FIB table (cefPeerFIBTable).

CEF Peer FIB Table--Cisco Express Forwarding Operation and Associated MIB Object

Cisco Express Forwarding Operation

MIB Objects

Gets the current Cisco Express Forwarding FIB operation state of the peer entity

cefPeerFIBOperState

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Prefix Length Statistics table (cefStatsPrefixTable).

CEF Prefix Length Statistics Table--Cisco Express Forwarding Operations and Associated MIB Objects

Cisco Express Forwarding Operation

MIB Object

Gets the number of queries (lookups) in the FIB database for a prefix length

cefStatsPrefixQueries

Gets the number of queries (lookups) in the FIB database for a prefix length in a 64-bit value

cefStatsPrefixHCQueries

Gets the number of inserts in the FIB database for a prefix length

cefStatsPrefixInserts

Gets the number of inserts in the FIB database for a prefix length in a 64-bit value

cefStatsPrefixHCInsert

Gets the number of deletes in the FIB database for a prefix length

cefStatsPrefixDeletes

Gets the number of deletes in the FIB database for a prefix length in a 64-bit version

cefStatsPrefixHCDeletes

Gets the number of elements in the FIB database for a prefix length

cefStatsPrefixElements

Gets the number of elements in the FIB database for a prefix length in a 64-bit value

cefStatsPrefixHCElements

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Switching Statistics table (cefSwitchingStatsTable).

CEF Switching Statistics Table--Cisco Express Forwarding Operations and Associated MIB Objects

Cisco Express Forwarding Operation

MIB Objects

Gets the switching path of a Cisco Express Forwarding instance

cefSwitchingPath

Gets the number of packets dropped by a Cisco Express Forwarding instance

cefSwitchingDrop

Gets the number of packets dropped by a Cisco Express Forwarding instance in a 64-bit value

cefSwitchingHCDrop

Gets the number of packets that could be punted

cefSwitchingPunt

Gets the number of packets that could be punted in a 64-bit value

cefSwitchingHCPunt

Gets the number of packets that are punted to the host

cefSwitchingPunt2Host

Gets the number of packets that are punted to the host in a 64-bit value

cefSwitchingHCPunt2Host

The table below lists the Cisco Express Forwarding configuration and monitoring operations and associated MIB objects provided by the CEF IP Prefix Consistency Global Checker group (cefCCGlobalTable).

CEF IP Prefix Consistency Global Checker Group--Cisco Express Forwarding Operations and Associated MIB Objects

Cisco Express Forwarding Operation

MIB Objects

Enables or disables auto repairing of the consistency checkers

cefCCGlobalAutoRepairEnabled

Gets or sets the consistency checker wait time before fixing the inconsistency

cefCCGlobalAutoRepairDelay

Gets or sets the consistency checker wait time to reenable auto repair after auto repair runs

cefCCGlobalAutoRepairHoldDown

Enables or disables error message generation for an inconsistency

cefCCGlobalErrorMsgEnabled

The table below lists the Cisco Express Forwarding configuration and monitoring operations and associated MIB objects provided by the CEF Consistency Checker Type table (cefCCTypeTable).

CEF Consistency Checker Type Table--Cisco Express Forwarding Operations and Associated MIB Objects

Cisco Express Forwarding Operation

MIB Objects

Enables or disables the passive consistency checker

cefCCEnabled

Gets or sets the maximum number of prefixes per scan

cefCCCount

Gets or sets the period between scans for the consistency checker

cefCCPeriod

Gets the number of prefix consistency queries sent to the Cisco Express Forwarding FIB

cefCCQueriesSent

Gets the number of prefix consistency queries ignored by the consistent checker

cefCCQueriesIgnored

Gets the number of prefix consistent queries iterated back to the database

cefCCQueriesIterated

Gets the number of prefix consistent queries processed

cefCCQueriesChecked

The table below lists the Cisco Express Forwarding configuration and monitoring operations and associated MIB objects provided by the CEF Inconsistency Record table (cefInconsistencyRecordTable).

CEF Inconsistency Record Table--Cisco Express Forwarding Operations and Associated MIB Objects

Cisco Express Forwarding Operation

MIB Objects

Gets the network prefix type for the inconsistency

cefInconsistencyPrefixType

Gets the network prefix address for the inconsistency

cefInconsistencyPrefixAddr

Gets the network prefix length for the inconsistency

cefInconsistencyPrefixLen

Gets the VRF name for the inconsistency

cefInconsistencyVrfName

Gets the consistency checker type that found the inconsistency

cefInconsistencyCCType

Gets the entity in which this inconsistency occurred

cefInconsistencyEntity

Gets the reason for generating the inconsistency

cefInconsistencyReason

- missing (1)

- checksumErr (2)

- unknown (3)

Global Objects for Cisco Express Forwarding Inconsistency

Gets the value of the system uptime at the time an inconsistency was detected

entLastInconsistencyDetectTime

Sets an object to restart all active consistency checkers

cefInconsistencyReset

Gets the status of the inconsistency reset request

cefInconsistencyResetStatus

CISCO-CEF-MIB Notifications

The table below lists the Cisco Express Forwarding operations associated with the CISCO-CEF-MIB objects that enable the sending of Cisco Express Forwarding notifications.

Cisco Express Forwarding Notifications--Cisco Express Forwarding Operations and CISCO-CEF-MIB Objects That Enable Them

Cisco Express Forwarding Operation

MIB Object

Enables the sending of a notification on the detection of a Cisco Express Forwarding resource failure

cefResourceFailureNotifEnable

Enables the sending of a notification on the detection of a Cisco Express Forwarding peer state change

cefPeerStateChangeNotifEnable

Enables the sending of a notification on the detection of a Cisco Express Forwarding FIB peer state change

cefPeerFIBStateChangeNotifEnable

Sets the period of time after the sending of each notification event

cefNotifThrottlingInterval

Enables the sending of a notification on the detection of an inconsistency

cefInconcsistencyNotifEnable

You can enable or disable these notifications through the MIB or by entering a CLI command. The table below contains a description of the notifications and the commands you use to enable each notification.

Note

You must enter a snmp-server host command before you enter a command to enable or disable a CISCO-CEF-MIB notification.

Description of Notifications and Enabling Commands for the CEF-PROVISION-MIB Notifications

Notification

Generated for

Commands

Cisco Express Forwarding resource failure notification

A malloc failure, an Inter-Process Communication (IPC) failure, and any other type of failure related to External Data Representation (XDR) messages

CLI: snmp-server enable traps cef resource-failure

MIB: setany version ip-address community-string cefResourceFailureNotifEnable.0 -i 1

Cisco Express Forwarding peer state change notification

A change in the operational state of a peer on the line cards

CLI: snmp-server enable traps cef peer-state-change

MIB: setany version ip-address community-string cefPeerStateChangeNotifEnable.0 -i 1

Cisco Express Forwarding peer FIB state change notification

A change in the operational state of the peer FIB

CLI: snmp-server enable traps cef peer-fib-state-change

MIB: setany version ip-address community-string cefPeerFIBStateChangeNotifEnable.0 -i 1

Cisco Express Forwarding inconsistency detection notification

An inconsistency detected by the consistency checkers

CLI: snmp-server enable traps cef inconsistency

MIB: setany version ip-address community-string cefInconsistencyNotifEnable.0 -i 1

How to Configure SNMP CEF-MIB Support

- Configuring the Router to Use SNMP

- Configuring a Host to Receive Notifications

- Configuring SNMP Notifications with the CLI

- Configuring SNMP Notifications with SNMP Commands

- Configuring the Throttling Interval with the CLI

- Configuring the Throttling Interval using SNMP Commands

Configuring the Router to Use SNMP

Perform the following task to configure a router to use SNMP.

Before you can use the Cisco Express Forwarding--SNMP CEF-MIB Support feature, you must configure the SNMP server for the router.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    snmp-server community string [view view-name] [ro | rw] [ipv6 nacl] [access-list-number]

4.    snmp-server community string2 rw

5.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

snmp-server community string [view view-name] [ro | rw] [ipv6 nacl] [access-list-number]

Example:

Router(config)# snmp-server community public ro

Sets up the community access string to permit access to SNMP.

- The string argument is a community string that consists of from 1 to 32 alphanumeric characters and functions much like a password, permitting access to the SNMP protocol. Blank spaces are not permitted in the community string.

- The view view-name keyword-argument pair is the name of a previously defined view. The view defines the objects available to the SNMP community.

- The ro keyword specifies read-only access. Authorized management stations can only retrieve MIB objects.

- The rw keyword specifies read-write access. Authorized management stations can retrieve and modify MIB objects.

- The ipv6 naclkeywords specify the IPv6 named access list.

- The access-list-number argument is an integer from 1 to 99. It specifies a standard access list of IP addresses or a string (not to exceed 64 characters) that is the name of a standard access list of IP addresses that are allowed access to the SNMP agent.

Alternatively, an integer from 1300 to 1999 that specifies a list of IP addresses in the expanded range of standard access list numbers. Devices at these addresses are allowed to use the community string to gain access to the SNMP agent.

Note:
The stringargument (Step 3) and string2argument (Step 4) provide a minimal level of security. It is advisable to provide the string for read-only access to others who need only to view and not to modify the MIB objects, and reserve the read-write access string for administrators only. The string2 argument (Step 4) should be different from the read-only string argument specified in this step.

Step 4

snmp-server community string2 rw

Example:

Router(config)# snmp-server community private rw

Sets up the community access string to permit access to SNMP.

- The string2 argument is a community string that consists of from 1 to 32 alphanumeric characters and functions much like a password, permitting access to the SNMP protocol. Blank spaces are not permitted in the community string.

- The rw keyword specifies read-write access. Authorized management stations can retrieve and modify MIB objects.

This example allows MIB objects to be retrieved and set because a string is specified with read-write access.

Note:
The stringargument (Step 3) and string2argument (Step 4) provide a minimal level of security. It is advisable to provide the string for read-only access to others who need only to view and not to modify the MIB objects, and reserve the read-write access string for administrators only. The string2 argument (Step 4) should be different from the read-only string argument specified in the preceding step (Step 3).

Step 5

end

Example:

Router(config)# end

Exits to privileged EXEC mode.

Configuring a Host to Receive Notifications

Perform the following task to configure an SNMP host to receive CISCO-CEF-MIB notifications. Notifications provide information to assist you in the monitoring and managing of Cisco Express Forwarding operations.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    snmp-server community string [ro | rw]

4.    snmp-server community string2 rw

5.    snmp-server host ip-address [vrf vrf-name] [traps | informs] [version {1| 2c | 3 [auth | noauth | priv]}] community-string [udp-port port] cef

6.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

snmp-server community string [ro | rw]

Example:

Router(config)# snmp-server community public ro

Sets up the community access string to permit access to SNMP.

- The string argument is a community string that consists of from 1 to 32 alphanumeric characters and functions much like a password, permitting access to the SNMP protocol. Blank spaces are not permitted in the community string.

- The ro keyword specifies read-only access. Authorized management stations can only retrieve MIB objects.

- The rw keyword specifies read-write access. Authorized management stations can retrieve and modify MIB objects.

Step 4

snmp-server community string2 rw

Example:

Router(config)# snmp-server community private rw

Sets up the community access string to permit access to SNMP.

- The string2 argument is a community string that consists of from 1 to 32 alphanumeric characters and functions much like a password, permitting access to the SNMP protocol. Blank spaces are not permitted in the community string.

- The rw keyword specifies read-write access. Authorized management stations can retrieve and modify MIB objects.

This example allows MIB objects to be retrieved and set because a string is specified with read-write access.

Note:
The stringargument (Step 3) and string2argument (Step 4) provide a minimal level of security. It is advisable to provide the string for read-only access to others who need only to view and not to modify the MIB objects, and retain the read-write access string for administrators only. The string2 argument (Step 4) should be different from the read-only string argument specified in the preceding step (Step 3).

Step 5

snmp-server host ip-address [vrf vrf-name] [traps | informs] [version {1| 2c | 3 [auth | noauth | priv]}] community-string [udp-port port] cef

Example:

Router(config)# snmp-server host 10.56.125.47 informs version 2c public cef

Specifies the recipient of an SNMP notification operation.

- The ip-address argument is the IP address or IPv6 address of the SNMP notification host.

The SNMP notification host is typically a network management station (NMS or SNMP manager). This host is the recipient of the SNMP traps or informs.

- The vrf vrf-name keyword and argument specify that the specified VRF be used to send SNMP notifications.

- The traps keyword specifies that notifications should be sent as traps. This is the default.

- The informs keyword specifies that notifications should be sent as informs.

- The version keyword specifies the version of the SNMP used to send the traps. The default is 1.

If you use the version keyword, one of the following keywords must be specified:

- 1 --SNMPv1. This option is not available with informs.

- 2c --SNMPv2c.

- 3 --SNMPv3. The most secure model because it allows packet encryption with the priv keyword. The default is noauth.

- One of the following three optional security level keywords can follow the version 3 keywords:

- auth--Enables Message Digest 5 (MD5) and Secure Hash Algorithm (SHA) packet authentication.

- noauth--Specifies that the noAuthNoPriv security level applies to this host. This is the default security level for SNMPv3.

- priv--Enables Data Encryption Standard (DES) packet encryption (also called "privacy").

- The community-string argument specifies that a password-like community string be sent with the notification operation.

- The udp-port port keyword and argument specify that SNMP notifications or informs are to be sent to the User Datagram Protocol (UDP) port number of the NMS host. The default is 162.

- The cef keyword specifies that the Cisco Express Forwarding notification type is to be sent to the host. If no type is specified, all available notifications are sent.

Step 6

end

Example:

Router(config)# end

Exits to privileged EXEC mode.

Configuring SNMP Notifications with the CLI

Perform the following task to configure SNMP notifications for Cisco Express Forwarding events. To configure this feature using SNMP commands instead of the CLI, see the Configuring SNMP Notifications with SNMP Commands.

Before You Begin

You must have configured an NMS or SNMP agent to receive the SNMPCISCO-CEF-MIB notification. See the Configuring a Host to Receive Notifications.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    snmp-server enable traps cef [peer-state-change] [resource-failure] [inconsistency] [peer-fib-state-change]

4.    snmp-server host ip-address [traps | informs] [version {1| 2c | 3 [auth | noauth | priv]}] community-string cef

5.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

snmp-server enable traps cef [peer-state-change] [resource-failure] [inconsistency] [peer-fib-state-change]

Example:

Router(config)# snmp-server enable traps cef resource-failure

Enables Cisco Express Forwarding support of SNMP notifications on an NMS.

- The peer-state change keyword enables the sending of CISCO-CEF-MIB SNMP notifications for changes in the operational state of Cisco Express Forwarding peers.

- The resource-failure keyword enables the sending of CISCO-CEF-MIB SNMP notifications for resource failures that affect Cisco Express Forwarding operations.

- The inconsistencykeyword enables the sending of CISCO-CEF-MIB SNMP notifications for inconsistencies that occur when routing information is updated from the Routing Information Base (RIB) to the CISCO-CEF-MIB on the RP and to the CISCO-CEF-MIB on the line cards.

You can set the throttling interval for sending inconsistency notifications. See the Configuring the Throttling Interval with the CLI.

- The peer-fib-state-change keyword enables the sending of CISCO-CEF-MIB SNMP notifications for changes in the operational state of the Cisco Express Forwarding peer FIB.

Step 4

snmp-server host ip-address [traps | informs] [version {1| 2c | 3 [auth | noauth | priv]}] community-string cef

Example:

Router(config)# snmp-server host 10.56.125.47 informs version 2c public cef

Specifies the recipient of an SNMP notification operation.

- The ip-address argument is the IP address or IPv6 address of the SNMP notification host.

The SNMP notification host is typically a network management station (NMS or SNMP manager). This host is the recipient of the SNMP traps or informs.

- The traps keyword specifies that notifications should be sent as traps. This is the default.

- The informs keyword specifies that notifications should be sent as informs.

- The version keyword specifies the version of the SNMP used to send the traps or informs. The default is 1.

If you use the version keyword, one of the following keywords must be specified:

- 1 --SNMPv1. This option is not available with informs.

- 2c --SNMPv2C.

- 3 --SNMPv3. The most secure model because it allows packet encryption with the priv keyword. The default is noauth.

- One of the following three optional security level keywords can follow the version 3 keywords:

- auth--Enables Message Digest 5 (MD5) and Secure Hash Algorithm (SHA) packet authentication.

- noauth--Specifies that the noAuthNoPriv security level applies to this host. This is the default security level for SNMPv3.

- priv--Enables Data Encryption Standard (DES) packet encryption (also called "privacy").

- The community-string argument specifies that a password-like community string be sent with the notification operation.

- The cef keyword specifies that the Cisco Express Forwarding notification type is to be sent to the host. If no type is specified, all available notifications are sent.

Step 5

end

Example:

Router(config)# end

Exits to privileged EXEC mode.

Configuring SNMP Notifications with SNMP Commands

Perform the following task to configure SNMP notifications for Cisco Express Forwarding events. To configure this feature using the CLI instead of SNMP commands, see the Configuring SNMP Notifications with the CLI.

Before You Begin

You must have configured an NMS or SNMP agent to receive the SNMPCISCO-CEF-MIB notification. See the Configuring a Host to Receive Notifications.

SUMMARY STEPS

1.    setany version ip-address community-string cefPeerStateChangeNotifEnable.0 -i TruthValue

2.    setany version ip-address community-string cefPeerFIBStateChangeNotifEnable .0 -i TruthValue

3.    setany version ip-address community-string cefResourceFailureNotifEnable. 0 -i TruthValue

4.    setany version ip-address community-string cefInconsistencyNotifEnable .0 -i TruthValue

DETAILED STEPS

Command or Action

Purpose

Step 1

setany version ip-address community-string cefPeerStateChangeNotifEnable.0 -i TruthValue

Example:

workstation% setany -v2c 10.56.125.47 public cefPeeStateStateChangeNotifEnable.0 -1 1

Enables the sending of CISCO-CEF-MIB SNMP notifications for changes in operational state of Cisco Express Forwarding peers.

- The version argument specifies the version of SNMP that is used. Options are

- -v1--SNMPv1

- -v2c--SNMPv2C

- -v3--SNMPv3

- The ip-address argument is the IP address or IPv6 address of the SNMP notification host.

The SNMP notification host is typically a network management station (NMS or SNMP manager). This host is the recipient of the SNMP traps or informs.

- The community-string argument specifies that a password-like community string be sent with the notification operation.

- The -ikeywords indicate that the variable that follows is an integer.

- Values for the TruthValue argument are:

- 1--enable sending of the notification

- 2--disable sending of the notification

These arguments and keywords apply to the Cisco-CEF-MIB notifications in Steps 2, 3, and 4.

Step 2

setany version ip-address community-string cefPeerFIBStateChangeNotifEnable .0 -i TruthValue

Example:

workstation% setany -v2c 10.56.125.47 public cefPeerFIBStateChangeNotifEnable.0 -1 1

Enables the sending of CISCO-CEF-MIB SNMP notifications for changes in the operational state of the Cisco Express Forwarding peer FIB.

- See Step 1 for a description of the command arguments and keywords.

Step 3

setany version ip-address community-string cefResourceFailureNotifEnable. 0 -i TruthValue

Example:

workstation% setany -v2c 10.56.125.47 public cefResourceFailureNotifEnable.0 -i 1

Enables the sending of CISCO-CEF-MIB SNMP notifications for resource failures that affect Cisco Express Forwarding operations.

- See Step 1 for a description of the command arguments and keywords.

Step 4

setany version ip-address community-string cefInconsistencyNotifEnable .0 -i TruthValue

Example:

workstation% setany -v2c 10.56.125.47 public cefInconsistencyNotifEnable.0 -i 1

Enables the sending of CISCO-CEF-MIB SNMP notifications for inconsistencies that occur when routing information is updated from the RIB to the Cisco Express Forwarding FIB on the RP and to the Cisco Express Forwarding FIB on the line cards.

- See Step 1 for a description of the command arguments and keywords.

Configuring the Throttling Interval with the CLI

Perform the following task to configure the throttling interval for CISCO-CEF-MIB inconsistency notifications. To configure this feature using SNMP commands instead of the CLI, see the Configuring the Throttling Interval with SNMP Commands section.

Configuring a throttling interval allows some time before an inconsistency notification is sent during the process of updating forwarding information from the Routing Information Base (RIB) to the RP and to the line card databases. As these databases are updated, inconsistencies might occur as a result of the asynchronous nature of the distribution mechanism for these databases. The throttling interval allows fleeting inconsistencies to resolve themselves before an inconsistency notification is sent.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    snmp-server enable traps cef inconsistency

4.    snmp mib cef throttling-interval seconds

5.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

- Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

snmp-server enable traps cef inconsistency

Example:

Router(config)# snmp-server enable traps cef inconsistency

Enables the sending of CISCO-CEF-MIB SNMP notifications for inconsistencies in Cisco Express Forwarding.

Step 4

snmp mib cef throttling-interval seconds

Example:

Router(config)# snmp mib cef throttling-interval 2500

Sets the throttling interval for the CISCO-CEF-MIB inconsistency notifications.

- The seconds argument is the time to allow before an inconsistency notification is sent during the process of updating forwarding information from the RIB to the RP and to the line card databases. A valid value is from 0 to 3600 seconds. A value of 0 disables throttle control.

Step 5

end

Example:

Router(config)# end

Exits to privileged EXEC mode.

Configuring the Throttling Interval using SNMP Commands

Perform the following task to configure the throttling interval for CISCO-CEF-MIB inconsistency notifications. To configure this feature using the CLI instead of SNMP commands, see the Configuring the Throttling Interval with the CLI.

Configuring a throttling interval allows some time before an inconsistency notification is sent during the process of updating forwarding information from the Routing Information Base (RIB) to the RP and to the line card databases. As these databases are updated, inconsistencies might occur as a result of the asynchronous nature of the distribution mechanism for these databases. The throttling interval allows fleeting inconsistencies to resolve themselves before an inconsistency notification is sent.

SUMMARY STEPS

1.    setany version ip-address community-string cefNotifThrottlingInterval.0 -i seconds

DETAILED STEPS

Command or Action

Purpose

Step 1

setany version ip-address community-string cefNotifThrottlingInterval.0 -i seconds

Example:

workstation% setany -v2c 10.56.125.47 public cefNotifThrottlingInterval.0 -1 3600

Sets the throttling interval for the CISCO-CEF-MIB inconsistency notifications.

- The version argument specifies the version of SNMP that is used. Options are

- -v1--SNMPv1

- -v2c--SNMPv2C

- -v3--SNMPv3

- The ip-address argument is the IP address or IPv6 address of the SNMP notification host.

The SNMP notification host is typically a network management station (NMS or SNMP manager). This host is the recipient of the SNMP traps or informs.

- The community-string argument specifies that a password-like community string be sent with the notification operation.

- The -ikeywords indicate that the variable that follows is an integer.

- The seconds argument is the time to allow before an inconsistency notification is sent during the process of updating forwarding information from the RIB to the RP and to the line card databases. A valid value is from 0 to 3600 seconds. A value of 0 disables throttle control.

Configuration Examples for SNMP CEF-MIB Support

- Example Configuring a Host to Receive Notifications

- Example Configuring SNMP Notifications

- Example Configuring the Throttling Interval

Example Configuring a Host to Receive Notifications

The following example shows how to configure an SNMP host to receive CISCO-CEF-MIB notifications:

configure terminal
!

snmp-server community public ro

snmp-server community private rw

snmp-server host 10.56.125.47 informs version 2vc public cef

end

This example sets up SNMP host 10.56.125.47 to receive CISCO-CEF-MIB notifications as informs.

Example Configuring SNMP Notifications

This section contains examples for configuring SNMP notifications for Cisco Express Forwarding events using the CLI and using SNMP commands.

Configuring SNMP Notifications for Cisco Express Forwarding Events Using the CLI

This example shows how to use the CLI to configure CISCO-CEF-MIB SNMP notifications to be sent to host 10.56.125.47 as informs for changes in Cisco Express Forwarding peer states and peer FIB states, for Cisco Express Forwarding resource failures, and for inconsistencies in Cisco Express Forwarding events:

configure terminal
!

snmp-server community public ro

snmp-server host 10.56.125.47 informs version 2c public cef

!
snmp-server enable traps cef peer-state-change
snmp-server enable traps cef peer-fib-state-change
snmp-server enable traps cef inconsistency
snmp-server enable traps cef resource-failure
end

Configuring SNMP Notifications for Cisco Express Forwarding Events Using SNMP Commands

This example shows the use of SNMP command to configure CISCO-CEF-MIB SNMP notifications to be sent to host 10.56.125.47 for changes in Cisco Express Forwarding peer states and peer FIB states, for Cisco Express Forwarding resource failures, and for inconsistencies in Cisco Express Forwarding events:

setany -v2c 10.56.125.47 public cefPeerStateChangeNotifEnable.0 -i 1

setany -v2c 10.56.125.47 public cefPeerFIBStateChangeNotifEnable.0 -i 1

setany -v2c 10.56.125.47 public cefResourceFailureNotifEnable.0 -i 1
setany -v2c 10.56.125.47 public cefInconsistencyNotifEnabled.0 -i 1

Example Configuring the Throttling Interval

This example shows the configuration of a throttling interval for the sending of Cisco Express Forwarding inconsistency notifications to the SNMP host using CLI commands and SNMP commands. The throttling interval is the amount of time that passes between the time that the inconsistency occurs and the sending of the notification to the SNMP host.

Configuring the Throttling Interval for CISCO-CEF-MIB Inconsistency Notifications Using CLI Commands

This example shows the addition of a throttling interval of 1000 seconds for the sending of Cisco Express Forwarding inconsistency notifications to the SNMP host using CLI commands:

configure terminal
!

snmp-server community public ro

snmp-server host 10.56.125.47 informs version 2c public cef

!
snmp-server enable traps cef peer-state-change
snmp-server enable traps cef peer-fib-state-change
snmp-server enable traps cef inconsistency
snmp-server enable traps cef resource-failure
!
snmp mib cef throttling-interval 1000
end

Configuring the Throttling Interval for CISCO-CEF-MIB Inconsistency Notifications Using SNMP Commands

This example shows the addition of a throttling interval of 1000 seconds for the sending of Cisco Express Forwarding inconsistency notifications to the SNMP host using an SNMP command:

setany -v2c 10.56.125.47 public cefNotifThrottlingInterval.0 -1 1000

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

IP switching commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples.

Cisco IOS IP Switching Command Reference

Overview of Cisco Express Forwarding, and links to related Cisco Express Forwarding documents

"Cisco Express Forwarding Overview" module

Standards

Standard

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

--

MIBs

MIB

MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

Click Here

RFCs

RFC

Title

RFC 3291

Textual Conventions for Internet Network Addresses

RFC 3413

Simple Network Management Protocol (SNMP) Applications

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

Click Here

Feature Information for SNMP CEF-MIB Support

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.

Feature Information for Cisco Express Forwarding--SNMP CEF-MIB Support

Feature Name

Release

Feature Information

Cisco Express Forwarding--SNMP CEF-MIB Support

12.2(31)SB2 12.2(33)SRC 12.2(33)SB 12.4(20)T 15.0(1)M 12.2(33)SRE 12.2(50)SY

The Cisco Express Forwarding--SNMP CEF-MIB Support feature introduces the CISCO-CEF-MIB that allows management applications through the use of the Simple Network Management Protocol (SNMP) to configure and monitor Cisco Express Forwarding operational data and to provide notification when Cisco Express Forwarding encounters specific configured events. This module describes how to use the CISCO-CEF-MIB to manage and monitor objects related to Cisco Express Forwarding operation.

The following commands were introduced or modified: snmp mib cef throttling-interval, snmp-server enable traps cef, snmp-server host.

Glossary

inform --A type of notification message that is more reliable than a conventional trap notification message because the informs message notification requires acknowledgment, but a trap notification does not.

IPC --Inter-Process Communication. The protocol used by routers that support distributed packet forwarding. The Cisco IOS version of IPC provides a reliable ordered delivery of messages using an underlying platform driver transport or User Date Protocol (UDP) transport protocol. Cisco IOS software IPC services allow line cards (LCs) and the central route processor (RP) in a distributed system, such as a Cisco 7500 series router, to communicate with each other by exchanging messages from the RP to the LCs. Communication messages are also exchanged between active and standby RPs. The IPC messages include configuration commands, responses to the configuration commands, and other events that are reported by an LC to the RP.

MIB --Management Information Base. A database of network management information that is used and maintained by a network management protocol such as Simple Network Management Protocol (SNMP). The value of a MIB object can be changed or retrieved by the use of SNMP commands, usually through a network management system. MIB objects are organized in a tree structure that includes public (standard) and private (proprietary) branches.

NMS --network management station. A powerful, well-equipped computer (typically an engineering workstation) that is used by a network administrator to communicate with other devices in the network. An NMS is typically used to manage network resources, gather statistics, and perform a variety of network administration and configuration tasks. In the context of SNMP, an NMS is a device that performs SNMP queries to the SNMP agent of a managed device to retrieve or modify information.

notification --A message sent by a Simple Network Management Protocol (SNMP) agent to a network management station, console, or terminal to indicate that a significant network event has occurred.

SNMP --Simple Network Management Protocol. A network management protocol used almost exclusively in TCP/IP networks. SNMP enables a user to monitor and control network devices, manage configurations, collect statistics, monitor performance, and ensure network security.

SNMP community --An authentication scheme that enables an intelligent network device to validate SNMP requests.

SNMPv2c --Version 2c of the Simple Network Management Protocol. SNMPv2c supports centralized as well as distributed network management strategies and includes improvements in the Structure of Management Information (SMI), protocol operations, management architecture, and security.

SNMPv3 --Version 3 of the Simple Network Management Protocol. Interoperable standards-based protocol for network management. SNMPv3 provides secure access to devices by a combination of authenticating and encrypting packets over the network.

trap --A message sent by an SNMP agent to a network management station, console, or terminal to indicate that a significant network event has occurred. Traps are less reliable than inform requests, because the receiver of the trap does not send an acknowledgment of receipt; furthermore, the sender of the trap cannot determine if the trap was received.

Chapter 11. Cisco Express Forwarding Command Changes

This feature module details changes to commands that are required to support updates to Cisco Express Forwarding.

In Cisco IOS Releases 12.2(25)S, 12.2(28)SB, 12.2(33)SRA, 12.2(33)SXH, and 12.4(20)T, Cisco Express Forwarding has been updated to support new features and new hardware. These updates enable Cisco Express Forwarding to operate with the Multiprotocol Label Switching (MPLS) High Availability (HA) applications and the MPLS Forwarding Infrastructure (MFI).

Cisco Express Forwarding provides a forwarding path and maintains a complete forwarding and adjacency table for both the software and hardware forwarding engines.

- Finding Feature Information

- Information About Command Changes

- Additional References

- Feature Information for Cisco Express Forwarding Command Changes

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to Click Here . An account on Cisco.com is not required.

Information About Command Changes

- Deleted Commands

- Replaced Commands

Deleted Commands

The following commands are obsolete and are no longer available from Cisco IOS Releases 12.2(25)S, 12.2(28)SB, 12.2(33)SRA, 12.2(33)SXH, 12.4(20)T, and future releases (no replacement commands are provided):

- clear adjacency epoch

- clear cef linecard events

- clear ip cef epoch

- clear ip cef events

- clear ip cef * prefix-statistics

- debug adjacency adjlist

- debug ip cef bulk-xfer

- debug ip cef elog-cef

- debug ip cef elog-plat

- debug ip cef stats

- ip cef switch

- ip cef linecard event-log

- ip cef linecard reloader

- ip cef load-sharing algorithm jittered

- ip cef nsf sync

- ip cef table event-log

- ip cef table resolution-timer

- ip cef table short-mask-protection

- show cef events

- show cef linecard events

Replaced Commands

The table below lists all replaced Cisco Express Forwarding commands, starting with Cisco IOS Releases 12.2(25)S, 12.2(28)SB, 12.2(33)SRA, 12.2(33)SXH, and 12.4(20)T, for the Cisco 7500 series routers:

Replaced Cisco Express Forwarding Commands--Cisco 7500 Series Routers

Command

Replacement Command

ip cef table consistency-check

cef table consistency-check

debug ip cef adjfib

debug cef fib attached export

ip cef switch

ip cef

clear ip cef event-log

monitor event-trace cef ipv4 clear

ip cef linecard event-log max-events

monitor event-trace cef linecard size

show adjacency nexthop

show adjacency

show cef drop

show ip cef switching statistics

show cef not-cef-switched

show ip cef switching statistics

show cef events

show monitor event-trace

show ip cef events (still visible)

show monitor event-trace cef events

show cef events [internal]

show monitor event-trace cef events all

show cef linecard events

show monitor event-trace cef linecard

The table below lists all replaced Cisco Express Forwarding commands, starting with Cisco IOS Releases 12.2(25)S, 12.2(28)SB, 12.2(33)SRA, 12.2(33)SXH, and 12.4(20)T for the Cisco 10000 series routers:

Replaced Cisco Express Forwarding Commands--Cisco 10000 Series Routers

Command

Replacement Command

ip cef table consistency-check

cef table consistency-check

debug ip cef adjfib

debug cef fib attached export

clear ip cef event-log

monitor event-trace cef ipv4 clear

show adjacency nexthop

show adjacency

show cef drop

show ip cef switching statistics

show cef events

show monitor event-trace

show ip cef events (still visible)

show monitor event-trace cef events

show cef events [internal]

show monitor event-trace cef events all

show cef linecard events

-

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

IP switching commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples.

Cisco IOS IP Switching Command Reference

MPLS HA applications and MFI

MPLS High Availability: Overview

MIBs

MIB

MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

Click Here

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

Click Here

Feature Information for Cisco Express Forwarding Command Changes

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.

Feature Information for Cisco Express Forwarding: Command Changes

Feature Name

Releases

Feature Information

Cisco Express Forwarding: Command Changes

12.2(25)S 12.2(28)SB 12.2(33)SRA 12.2(33)SXH 12.4(20)T

In Cisco IOS Releases 12.2(25)S, 12.2(28)SB, 12.2(33)SRA and 12.2(33)SXH, Cisco Express Forwarding has been updated to support new features and new hardware. These updates enable Cisco Express Forwarding to operate with the Multiprotocol Label Switching (MPLS) High Availability (HA) applications and the MPLS Forwarding Infrastructure (MFI).

This feature module details changes to commands that are required to support updates to Cisco Express Forwarding.

In 12.2(25)S, this feature was introduced and supported on the Cisco 7500 series routers.

In 12.2(28)SB, this feature was integrated into Cisco IOS Release 12.2(28)SB and implemented on the Cisco 10000 series routers.

In 12.2(33)SRA, this feature was integrated into Cisco IOS Release 12.2(33)SRA.

In 12.2(33)SXH, this feature was integrated into Cisco IOS Release 12.2(33)SXH.

In 12.4(20)T, this feature was integrated into a Cisco IOS 12.4T release.

The following commands were modified: cef table consistency-check, clear adjacency, clear cef linecard, clear cef table, clear ip cef inconsistency, debug adjacency, debug cef, debug ip cef, debug ip cef accounting non-recursive, debug ip cef fragmentation, debug ip cef hash, debug ip cef subblock, debug ip cef table, ip route-cache, monitor event-trace (EXEC), monitor event-trace (global), show adjacency, show cef, show cef features global, show cef interface, show ip cef, show ip cef adjacency, show ip cef non-recursive, show ip cef switching statistics, show ip cef tree, show ip cef unresolved, show ip traffic, show monitor event-trace, show xdr.

Chapter 12. CEF Enhancements

The purpose of this document is to describe the changes based on the Cisco Express Forwarding infrastructure scalability enhancements that have been implemented to adapt to the evolution of the Internet and to support new platforms and features. The changes are the removal of IP fast switching and the introduction of command line interface (CLI) modifications.

This document lists Cisco Express Forwarding CLI commands that are removed, replaced, changed, and new. To help you transition to the new CLI format, the document illustrates the output for new commands and changed commands.

Enhancements to Cisco Express Forwarding enable it to operate with the Multiprotocol Label Switching (MPLS) Forwarding Infrastructure (MFI) and guarantee consistency across Cisco IOS release trains. Cisco Express Forwarding infrastructure changes were introduced and implemented in the Cisco IOS 12.2(25)S-based releases and were added for T releases in Cisco IOS Release 12.4(20)T.

Cisco Express Forwarding is an advanced Layer 3 IP switching technology. It optimizes network performance and scalability for all kinds of networks: those that carry small amounts of traffic and those that carry large amounts of traffic in complex patterns, such as the Internet, and networks characterized by intensive web-based applications or interactive sessions.

- Finding Feature Information

- Information About CEF

- Additional References

- Feature Information for CEF Enhancements

- Glossary

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to Click Here . An account on Cisco.com is not required.

Information About CEF

This document presents the following topics to explain the changes you will find with the implementation of the Cisco Express Forwarding enhancements. This information should be helpful as you transition to Cisco IOS software that includes the Cisco Express Forwarding and MFI enhancements.

The fifth and sixth topics provide information about the CLI changes implemented as part of the Cisco Express Forwarding enhancements. In each section, the commands that are changed are listed, followed by an explanation of how they are changed. Sample command output is included in sections to compare "before" and "after" output information and to provide new output information.

The information about the commands is presented in the following order:

- Removed or existing, but unsupported, commands

- Commands with modified output

- New commands created for output consistency

- Related commands with unchanged output

- Introduction of CEF Enhancements

- CEF Enhancements Described

- Removal of Support for IPv4 Fast Switching

- CEF Command Changes

- CEF show Command Output Changes

- New Commands for the CEF Feature

- Unchanged CEF show Commands

Introduction of CEF Enhancements

Cisco Express Forwarding is at the heart of switching in every router. Improvements have been made to the Cisco Express Forwarding infrastructure to enhance and scale switching. Cisco Express Forwarding enhancements were introduced in Cisco IOS Release 12.2(25)S and first adopted by Cisco IOS 12.2(25)S-based releases. In Cisco IOS Release 12.4(20)T, the Cisco Express Forwarding enhancements were added for Cisco IOS 12.4(20)T releases and later T-based releases.

The table below lists the Cisco IOS releases and platforms that support the Cisco Express Forwarding enhancements and the changes described in this document.

Cisco IOS Releases and Platforms That Support Cisco Express Forwarding Enhancements

Cisco IOS Release

Platforms Supported

12.2(25)SE

Catalyst 2970 series switches Catalyst 3500 series switches Catalyst 3750 series switches

12.2(25)SG

Catalyst 4500 series Switches

12.2(28)SB

Cisco 7200 series routers Cisco 7301 series routers Cisco 7304 series routers Cisco 10000 series routers

12.2(33)SRA

Cisco 7600 series routers

12.2(33)SXH

Catalyst 6500 series switches

12.4(20)T

Cisco 800 series routers Cisco 1700 series routers Cisco 1800 series routers Cisco 2600 series routers Cisco 2800 series routers Cisco 3200 series routers Cisco 3600 series routers Cisco 3700 series routers Cisco 3800 series routers Cisco 7200 series routers Cisco 7400 series routers Cisco 8850 series routers Cisco AS5000 series universal gateways

CEF Enhancements Described

Cisco IOS Release 12.4(20)T incorporates the following Cisco Express Forwarding infrastructure changes:

- Cisco Express Forwarding Scalability and Selective Rewrite (CSSR) for enhanced scalable, distributed Layer 3 switching

- Enhanced Multiprotocol Label Switching (MPLS) Forwarding Infrastructure (MFI)

For information on MFI enhancements, see MPLS Infrastructure Changes: Introduction of MFI and Removal of MPLS LSC and LC-ATM Features.

The Cisco Express Forwarding infrastructure changes provide the following:

- Simplified fast switching path decisions for both IPv4 and IPv6 traffic, which improve performance and provide more CPU cycles for other Cisco IOS services

- Enhanced scalability to support large numbers of the following:

- IPv4 and IPv6 prefixes and adjacencies

- Load balancing paths over multiple links based on Layer 3 routing information

- Virtual Private Network (VPN) routing and forwarding (VRF) instances

- Improved manageability of the following:

- Cisco Express Forwarding logging for both IPv4 and IPv6

- Unicast Reverse Path Forwarding (uRPF) strict and loose mode

- Cisco Express Forwarding MIB (CEF-MIB)

- uRPF MIB

- CLI display enhancements for Cisco Express Forwarding

No new features are introduced in Cisco IOS Release 12.4(20)T. However, some features that previously shipped with a Cisco IOS 12.2(25)S-based release are new to the Cisco IOS 12.4T release.

Note

CSSR and MFI enhancements in Cisco IOS Release 12.4(20)T might result in changed performance characteristics in your network. We suggest that you test configurations before upgrading to this software.

Removal of Support for IPv4 Fast Switching

IPv4 fast switching is removed with the implementation of the Cisco Express Forwarding infrastructure enhancements for Cisco IOS 12.2(25)S-based releases and Cisco IOS Release 12.4(20)T. For these and later Cisco IOS releases, switching path are Cisco Express Forwarding switched or process switched. This makes the switching decision easier for future development of software features.

Note

Starting with the implementation of the Cisco Express Forwarding enhancements and the removal of IPv4 fast switching, components that do not support Cisco Express Forwarding will work only in process switched mode.

CEF Command Changes

The following commands are obsolete and have been removed from Cisco IOS software with the present Cisco Express Forwarding enhancements:

- show ip cef inconsistency records

- show ip cef inconsistency now

- show ip cef inconsistency now detail

The table below lists the commands that replace the removed commands.

Removed Cisco Express Forwarding Commands--Cisco Express Forwarding

Command Before Cisco Express Forwarding Enhancements

Replacement Command After Cisco Express Forwarding Enhancements

ip cef table adjacency-prefix

--

ip cef table resolution-timer

--

show ip cef inconsistency records

test cef table consistency

show ip cef inconsistency now

test cef table consistency

show ip cef inconsistency now detail

test cef table consistency detail

The following commands still exist, but are no longer supported in Cisco IOS software:

- show cef events

- show cef dropped

- show cef non-cef-switched

The table below lists commands that still exist, but are no longer supported, and the commands that replaces the unsupported commands. You should start using the replacement commands.

Replaced Cisco Express Forwarding Commands--Cisco Express Forwarding Feature

Command Before Cisco Express Forwarding Enhancements

Replacement Command After Cisco Express Forwarding Enhancements

ip cef event -log

monitor event-log cef event

ip cef interface event-log

monitor event-log cef interface

ip cef table event-log

monitor event-log cef ipv4

ip cef table consistency-check

cef table consistency-check

ip cef loadinfo

cef table output-chain

show cef events

show monitor event-trace cef events all

show cef drop

show {ip | ipv6} cef switching statistics[feature][1]

show cef not-cef-switched

show {ip| ipv6} cef switching statistics [feature]

[1] If you enter the optional feature keyword, the output shows per-feature drop and punt counters.

CEF show Command Output Changes

This section describes the CLI command output changes introduced with the Cisco Express Forwarding feature. In some commands the output format is changed. In other commands, pieces of information are added or removed from the output. The output of the following commands is changed with this feature:

- show ip cef summary

- show ipv6 cef summary

- show ip cef internal

- show ipv6 cef internal

- show ip cef detail

- show ipv6 cef detail

- show ip cef internal

- show ipv6 cef internal

- show ip cef

- show ip cef exact-route detail

- show ip cef exact-route

- show ip cef adjacency

- show adjacency summary

- show adjacency detail

- show adjacency internal

- show cef state

- show cef timers

- show ip cef epoch

- show ipv6 cef epoch

- show ip cef unresolved detail

- show ipv6 cef unresolved detail

- show ipv6 cef non-recursive

For a full description of these commands, see the Cisco IOS IP Switching Command Reference and the Cisco IOS IPv6 Command Reference.

- show ip cef summary

- show ipv6 cef summary

- show ip cef internal

- show ipv6 cef internal

- show ip cef detail

- show ipv6 cef detail

- show ip cef internal

- show ipv6 cef internal

- show ip cef

- show ip cef exact-route detail

- show ip cef exact-route

- show ip cef adjacency

- show adjacency summary

- show adjacency detail

- show adjacency internal

- show cef state

- show cef timers

- show ip cef epoch

- show ipv6 cef epoch

- show ip cef unresolved detail

- show ipv6 cef unresolved detail

- show ipv6 cef non-recursive

show ip cef summary

This feature provides the following changes to the output of the show ip cef summary command:

- IPv4 and IPv6 are separately addressed.

- Figures related to adjacencies are moved to the show adjacency summarycommand (see the show adjacency summary).

- Mtrie data structure descriptions are moved to a new command, the show ip cef tree command (see the New Commands for the CEF Feature).

The table below compares the show ip cef summary command output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show ip cef summary Command Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show ip cef summary

IP CEF with switching (Table Version 32), flags=0x0

26 routes, 0 reresolve, 0 unresolved (0 old, 0 new), peak 2

26 leaves, 19 nodes, 23400 bytes, 53 inserts, 27 invalidations

0 load sharing elements, 0 bytes, 0 references

universal per-destination load sharing algorithm, id DF940F94

3(0) CEF resets, 0 revisions of existing leaves

Resolution Timer: Exponential (currently 1s, peak 1s)

0 in-place/0 aborted modifications

refcounts:  1342 leaf, 1321 node

Table epoch: 0 (26 entries at this epoch)

Adjacency Table has 4 adjacencies

2 IPv4 adjacencies

2 IPv6 adjacencies

Router# show ip cef summary

IPv4 CEF is enabled and running

VRF Default:

22 prefixes (22/0 fwd/non-fwd)

Table id 0

Database epoch:        0 (22 entries at this epoch)

show ipv6 cef summary

This feature provides the following change to the output of the show ipv6 cef summary command:

- Output is reformatted (information provided is similar to what was provided before the Cisco Express Forwarding enhancement.)

The table below compares the show ipv6 cef summary command output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show ipv6 cef summary Command Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show ipv6 cef summary

IPv6 CEF is enabled and running

Slow processing intvl = 1 seconds backoff level current/max 0/0

0 unresolved prefixes, 0 requiring adjacency update

IPv6 CEF default table

19 prefixes

Router# show ipv6 cef summary
IPv6 CEF is enabled and running
VRF Default:
20 prefixes (20/0 fwd/non-fwd)
Table id 0
Database epoch:        0 (20 entries at this epoch)

show ip cef internal

This feature provides the following changes to the output of the show ip cef internal command:

- IPv4 and IPv6 are separately addressed.

- Mtrie data structure descriptions are moved to a new command, the show ip cef tree command (see the New Commands for the CEF Feature).

- Troubleshooting is made easier with the addition of references to internal structure pointers.

- The concept of output chain (chain of output features) is introduced.

The table below compares the show ip cef internalcommand output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show ip cef internal Command Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show ip cef internal
IP CEF with switching (Table Version 32), flags=0x0
26 routes, 0 reresolve, 0 unresolved (0 old, 0 new), peak 2
26 leaves, 19 nodes, 23400 bytes, 53 inserts, 27 invalidations
0 load sharing elements, 0 bytes, 0 references
universal per-destination load sharing algorithm, id DF940F94
3(0) CEF resets, 0 revisions of existing leaves
Resolution Timer: Exponential (currently 1s, peak 1s)
0 in-place/0 aborted modifications
refcounts:  1342 leaf, 1321 node
Table epoch: 0 (26 entries at this epoch)
Adjacency Table has 3 adjacencies
1 IPv4 adjacency
2 IPv6 adjacencies
0.0.0.0/32, version 0, epoch 0, receive
10.10.1.1/32, version 22, epoch 0, cached adjacency 172.17.24.1 (0x629E1B60)
0 packets, 0 bytes
via 172.17.24.1, FastEthernet0/1, 0 dependencies
next hop 172.17.24.1, FastEthernet0/1
valid cached adjacency (0x629E1B60)

Router# show ip cef internal
IPv4 CEF is enabled and running
VRF Default:
22 prefixes (22/0 fwd/non-fwd)
Table id 0
Database epoch:        0 (22 entries at this epoch)
0.0.0.0/32, epoch 0, flags receive, refcount 4
sources: Spc
feature space:
MFI: path extension list empty
subblocks:
Special source: receive
ifnums: (none)
path 633AA3DC, path list 633A79D0, share 1, type receive
path_list contains no resolved destination(s). HW IPv4 notified.
receive
output chain: receive (11)
10.10.1.1/32, epoch 0, RIB, refcount 4
sources: RIB
feature space:
MFI: path extension list empty
IPRM: 0x00038000
IP adj out of POS1/0 635BB2A0
ifnums: (none)
path 633A9504, path list 633A6FB8, share 1, type attached nexthop
path_list contains at least one resolved destination(s). HW IPv4 notified.
nexthop 172.17.13.1 POS1/0, adjacency IP adj out of POS1/0 635BB2A0
output chain: IP adj out of POS1/0 635BB2A0

show ipv6 cef internal

This feature provides the following changes to the output of the show ipv6 cef internal command:

- More references to pointers are added.

- The concept of output chain (chain of output features) is introduced.

The previous version of the command output is very similar to the output of the command after the Cisco Express Forwarding enhancements.

The table below compares the show ipv6 cef internalcommand output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show ipv6 cef internal Command Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show ipv6 cef internal
IPv6 CEF is enabled and running
Slow processing intvl = 1 seconds backoff level current/max 0/0
0 unresolved prefixes, 0 requiring adjacency update
IPv6 CEF default table
19 prefixes tableid 0
table version 37
root 63038970
2001:1:12::/64 RIBfib
Using cached adjacency 0x629E1CE0
path list pointer 62A2C310
1 path -
Nexthop  path_pointer 62A297B0 traffic share 1 path_list pointer 62A2C310
nexthop FE80::2D0:1FF:FEE4:6800 FastEthernet0/1
next_hop_len 0 adjacency pointer 629E1CE0
refcount 10
no loadinfo

Router# show ipv6 cef internal

IPv6 CEF is enabled and running

VRF Default:

20 prefixes (20/0 fwd/non-fwd)

Table id 0

Database epoch:        0 (20 entries at this epoch)

2001:1:12::/64, epoch 0, RIB, refcount 3

sources: RIB

feature space:

MFI: path extension list empty

IPRM: 0x00038000

IPV6 adj out of POS1/0 635BAFE0

ifnums: (none)

path 633A9A18, path list 633A732C, share 1, type attached nexthop

path_list contains at least one resolved destination(s). HW IPv6 notified.

nexthop FE80::205:DCFF:FE26:4800 POS1/0, adjacency IPV6 adj out of POS1/0 635BAFE0

output chain: IPV6 adj out of POS1/0 635BAFE0

show ip cef detail

This feature provides the following changes to the output of the show ip cef detail command:

- IPv4 and IPv6 are now separately addressed.

- Mtrie data structure descriptions are moved to a new command, the show ip cef tree command (see the New Commands for the CEF Feature).

- The per-prefix output is reformatted (however, the information provided is the same).

- The table below compares the show ip cef detailcommand output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show ip cef detail Command Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show ip cef detail
IP CEF with switching (Table Version 32), flags=0x0
26 routes, 0 reresolve, 0 unresolved (0 old, 0 new), peak 2
26 leaves, 19 nodes, 23400 bytes, 53 inserts, 27 invalidations
0 load sharing elements, 0 bytes, 0 references
universal per-destination load sharing algorithm, id DF940F94
3(0) CEF resets, 0 revisions of existing leaves
Resolution Timer: Exponential (currently 1s, peak 1s)
0 in-place/0 aborted modifications
refcounts:  1342 leaf, 1321 node
Table epoch: 0 (26 entries at this epoch)
Adjacency Table has 3 adjacencies
1 IPv4 adjacency
2 IPv6 adjacencies
0.0.0.0/32, version 0, epoch 0, receive
10.10.1.1/32, version 22, epoch 0, cached adjacency 172.17.24.1
0 packets, 0 bytes
via 172.17.24.1, FastEthernet0/1, 0 dependencies
next hop 172.17.24.1, FastEthernet0/1
valid cached adjacency

Router# show ip cef detail
IPv4 CEF is enabled and running
VRF Default:
22 prefixes (22/0 fwd/non-fwd)
Table id 0
Database epoch:        0 (22 entries at this epoch)
0.0.0.0/32, epoch 0, flags receive
Special source: receive
receive
10.10.1.1/32, epoch 0
nexthop 172.17.13.1 POS1/0
10.10.1.2/32, epoch 0
nexthop 172.17.13.1 POS1/0
10.20.12.0/24, epoch 0
nexthop 172.17.13.1 POS1/0
10.60.17.0/24, epoch 0, flags attached, connected
attached to FastEthernet0/0
10.60.17.0/32, epoch 0, flags receive
receive
10.60.17.251/32, epoch 0, flags receive
receive

show ipv6 cef detail

This feature provides the following change to the output of the show ipv6 cef detail command:

- Output is reformatted (the information provided is the same as before the Cisco Express Forwarding enhancements).

The table below compares the show ipv6 cef detailcommand output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show ipv6 cef detail Command Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show ipv6 cef detail
IPv6 CEF is enabled and running
Slow processing intvl = 1 seconds backoff level current/max 0/0
0 unresolved prefixes, 0 requiring adjacency update
IPv6 CEF default table
19 prefixes
2001:1:12::/64 RIBfib
nexthop FE80::2D0:1FF:FEE4:6800 FastEthernet0/1
2001:2:13::/64 RIBfib
nexthop FE80::2D0:1FF:FEE4:6800 FastEthernet0/1
2001:2:22::/64 RIBfib
nexthop FE80::2D0:1FF:FEE4:6800 FastEthernet0/1
2001:2:24::2/128 Receive, RIBfib
Receive
2001:2:24::/64 Attached, Connected, RIBfib

attached to FastEthernet0/1

Router# show ipv6 cef detail
IPv6 CEF is enabled and running
VRF Default:
20 prefixes (20/0 fwd/non-fwd)
Table id 0
Database epoch:        0 (20 entries at this epoch)
2001:1:12::/64, epoch 0
nexthop FE80::205:DCFF:FE26:4800 POS1/0
2001:2:13::/64, epoch 0, flags attached, connected
attached to POS1/0
2001:2:13::2/128, epoch 0, flags receive

show ip cef internal

This feature provides the following changes to the output of the show ip cef prefix internal command:

- Troubleshooting is made easier with the addition of references to internal structure pointers.

- The concept of output chain (chain of output features) is introduced.

The table below compares the show ip cef prefix internal command output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show ip cef prefix internalCommand Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show ip cef 10.20.12.0/24
internal
10.20.12.0/24, version 17, epoch 0, cached adjacency 172.17.24.1 (0x629E1B60)
0 packets, 0 bytes
via 172.17.24.1, FastEthernet0/1, 0 dependencies
next hop 172.17.24.1, FastEthernet0/1
valid cached adjacency (0x629E1B60)

Router# show ip cef 172.16.1.0/24 internal
172.16.1.0/24, epoch 0, RIB, refcount 5
sources: RIB
feature space:
MFI: path extension list empty
IPRM: 0x00038000
IP adj out of POS1/0 635BB2A0
path 633A9504, path list 633A6FB8, share 1, type attached nexthop, for IPv4
ifnums: (none)
path_list contains at least one resolved destination(s). HW IPv4 notified.
nexthop 172.17.13.1 POS1/0, adjacency IP adj out of POS1/0 635BB2A0
output chain: IP adj out of POS1/0 635BB2A0

show ipv6 cef internal

This feature provides the following changes to the output of the show ipv6 cef prefix internal command:

- More references to structure pointers are added.

- The concept of output chain (chain of output features) is introduced.

The previous version of the command output is very similar to the output in the command after the Cisco Express Forwarding enhancements.

The table below compares the show ipv6 cef prefix internal command output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show ipv6 cef prefix internal Command Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show ipv6 cef 2001:2:25::/64 internal
2001:2:25::/64 RIBfib
Using cached adjacency 0x629E1CE0
path list pointer 62A2C310
1 path -
Nexthop  path_pointer 62A297B0 traffic share 1 path_list pointer 62A2C310
nexthop FE80::2D0:1FF:FEE4:6800 FastEthernet0/1
next_hop_len 0 adjacency pointer 629E1CE0
refcount 10
no loadinfo

Router# show ipv6 cef 2001:2:25::/64 internal
2001:2:25::/64, epoch 0, RIB, refcount 4
sources: RIB
feature space:
MFI: path extension list empty
IPRM: 0x00038000
IPV6 adj out of POS1/0 635BAFE0
path 633A9568, path list 633A6FFC, share 1, type attached nexthop, for IPv6
ifnums: (none)
path_list contains at least one resolved destination(s). HW IPv6 notified.
nexthop FE80::205:DCFF:FE26:4800 POS1/0, adjacency IPV6 adj out of POS1/0 635BAFE0

show ip cef

This feature provides the following changes to the output of the show ip cef prefix command:

- Output is reformatted; the key information provided is similar to the command output provided before the Cisco Express Forwarding enhancements.

- Adjacency information is moved to the show adjacency prefix detail command (see the New Commands for the CEF Feature).

The table below compares the show ip cef prefixcommand output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show ip cef prefix Command Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show ip cef 10.20.12.0/24
10.20.12.0/24, version 17, epoch 0, cached adjacency 172.17.24.1
0 packets, 0 bytes
via 172.17.24.1, FastEthernet0/1, 0 dependencies
next hop 172.17.24.1, FastEthernet0/1
valid cached adjacency

Router# show ip cef 172.16.1.0/24

172.16.1.0/24
nexthop 172.17.13.1 POS1/0

Note

The command output of the show ipv6 prefix command is the same after the Cisco Express Forwarding enhancement changes as it was before the changes.

show ip cef exact-route detail

This feature provides the following change to the output of the show ip cef exact-route source destination detail command:

- Output is reformatted (the information provided is the same as the information provided before the Cisco Express Forwarding enhancements).

The table below compares the command output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show ip cef exact-route source destination detail Command Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show ip cef exact-route 172.16.1.1 172.16.1.5 detail
172.16.1.1      -> 172.16.1.5     : FastEthernet0/1 (next hop 172.17.24.1)

Router# show ip cef exact-route 172.16.1.3 172.16.1.2 detail

172.16.1.3 -> 172.16.1.2 => IP adj out of FastEthernet0/1, addr 172.17.25.1

show ip cef exact-route

This feature provides the following change to the output of the show ip cef exact-route source destinationcommand:

- Output is reformatted (the information provided is the same as the information provided before the Cisco Express Forwarding enhancements).

The table below compares the show ip cef exact-route source destinationcommand output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show ip cef exact-route source destination Command Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show ip cef exact-route 172.16.1.1 172.16.1.5

172.16.1.1      -> 172.16.1.5     : FastEthernet0/1 (next hop 172.17.24.1)

Router# show ip cef exact-route 172.16.1.3 172.16.1.2

172.16.1.3 -> 172.16.1.2 => IP adj out of FastEthernet0/1, addr 172.17.25.1

show ip cef adjacency

This feature provides the following change to the output of the show ip cef adjacency interface next-hopcommand:

- Output is reformatted (the information provided is the same as the information provided before the Cisco Express Forwarding enhancements).

The table below compares the show ip cef adjacency interface next-hopcommand output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show ip cef adjacency interface next-hopCommand Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show ip cef adjacency FastEthernet0/1 172.17.24.1
Prefix              Next Hop             Interface
10.10.1.1/32        172.17.24.1          FastEthernet0/1
10.10.1.2/32        172.17.24.1          FastEthernet0/1
10.20.12.0/24       172.17.24.1          FastEthernet0/1

Router# show ip cef adjacency FastEthernet0/1 172.17.22.1
10.10.1.2/32
nexthop 172.17.22.1 FastEthernet0/1
10.20.12.0/24
nexthop 172.17.22.1 FastEthernet0/1

show adjacency summary

This feature provides the following change to the output of the show adjacency summary command:

- The new output provides a detailed description of the database, high availability information, and epoch concept information.

- The per-protocol and interface summary table is moved to the show adjacency linkcommand (see the New Commands for the CEF Feature).

The table below compares the show adjacency summary command output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show adjacency summary Command Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show adjacency summary
Adjacency Table has 6 adjacencies
4 IPv4 adjacencies
2 IPv6 adjacencies
Table epoch: 0 (6 entries at this epoch)
Interface                 IPv4 Adjacencies  IPv6 Adjacencies
FastEthernet0/1           1                 1
FastEthernet0/0           2                 0
FastEthernet1/1           1                 1

Router# show adjacency summary
Adjacency table has 9 adjacencies:
each adjacency consumes 348 bytes (0 bytes platform extension)
7 complete adjacencies
2 incomplete adjacencies
4 adjacencies of linktype IP
4 complete adjacencies of linktype IP
0 incomplete adjacencies of linktype IP
0 adjacencies with fixups of linktype IP
4 adjacencies with IP redirect of linktype IP
4 adjacencies of linktype IPV6
2 complete adjacencies of linktype IPV6
2 incomplete adjacencies of linktype IPV6
1 adjacency of linktype TAG
1 complete adjacency of linktype TAG
0 incomplete adjacencies of linktype TAG
Adjacency database high availability:
Database epoch: 0 (9 entries at this epoch)
Adjacency manager summary event processing:
Summary events epoch is 3
Summary events queue contains 0 events (high water mark 7 events)

show adjacency detail

This feature provides the following change to the output of the show adjacency detail command:

- Output is reformatted (the information provided is the same as the information provided before the Cisco Express Forwarding enhancements).

The table below compares the show adjacency detail command output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show adjacency detailCommand Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show adjacency detail
Protocol Interface           Address
IP       FastEthernet1/1     20.0.0.2(5)
4 packets, 456 bytes
003085641F11
00055F26F81D0800
ARP        01:47:23
Epoch: 0
IPV6     FastEthernet1/1     2011:41::2(5)
0 packets, 0 bytes
003085641F11
00055F26F81D86DD
IPv6 ND    never
Epoch: 0

Router# show adjacency detail
Protocol Interface           Address
IP       FastEthernet0/1     172.17.22.1(16)
0 packets, 0 bytes
epoch 0
sourced in sev-epoch 3
Encap length 14
00D001E4680000055FAF2C060800
ARP
IPV6     FastEthernet0/1     2001:2:22::1(6)
0 packets, 0 bytes
epoch 0
sourced in sev-epoch 3
Encap length 14
00D001E4680000055FAF2C0686DD
IPv6 ND

show adjacency internal

This feature provides the following changes to the output of the show adjacency internal command:

- Output is reformatted.

- An output chain of features was added. Otherwise, the information provided is the same as the information provided before the Cisco Express Forwarding enhancements.

The table below compares the show adjacency internalcommand output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show adjacency internal Command Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show adjacency internal
Protocol Interface          Address
IP       FastEthernet1/1    20.0.0.2(5)
4 packets, 456 bytes
003085641F11
00055F26F81D0800
ARP        01:32:30
Epoch: 0
Fast adjacency enabled
IP redirect enabled
IP mtu 1500 (0x0)
Fixup disabled
Adjacency pointer 0x629E16E0, refCount 5
Adjacency flags 0x000000
Connection Id 0x000000
Bucket 22
IPV6     FastEthernet0/1    FE80::2D0:1FF:FEE4:6800(13)
0 packets, 0 bytes
00D001E46800
00055F26F80686DD
IPv6 ND    never
Epoch: 0
Fast adjacency enabled
IPv6 redirect enabled
IPv6 mtu 1500 (0x0)
Fixup disabled
Adjacency pointer 0x629E1CE0, refCount 13
Adjacency flags 0x000000
Connection Id 0x000000

Bucket 32

Router# show adjacency internal

Protocol Interface          Address
IP       FastEthernet0/0    10.60.17.2(6)
0 packets, 0 bytes
epoch 0
sourced in sev-epoch 3
Encap length 14
00000C386D8800055FAF2C080800
ARP
Fast adjacency enabled [OK]
L3 mtu 1500
Flags (0x100E)
Fixup disabled
HWIDB/IDB pointers 0x63148358/0x63148FD8
IP redirect enabled
Switching vector: IPv4 no fixup adj oce
Adjacency pointer 0x636F31A0
Next-hop 172.17.13.1 ...
IPV6     FastEthernet0/1    2001:2:22::1(6)
0 packets, 0 bytes
epoch 0
sourced in sev-epoch 3
Encap length 14
00D001E4680000055FAF2C0686DD
IPv6 ND
Fast adjacency enabled [OK]
L3 mtu 1500
Flags (0x100E)
Fixup disabled
HWIDB/IDB pointers 0x6313AD40/0x6313B9C0
IP redirect enabled
Switching vector: IPv6 adjacency oce
Adjacency pointer 0x531C738
Next-hop FE80::A8BB:FE00:6500 ...

show cef state

This feature provides the following changes to the output of the show cef statecommand:

- New output is more concise.

- Load sharing anti-polarization ID is added to the command output.

- The show cef statecommand adds a new capabilities keyword. Capability details now display with the new keyword.

The table below compares the show cef statecommand output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show cef state Command Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show cef state
CEF Status [RP]
CEF enabled/running
dCEF disabled/not running
CEF switching enabled/running
CEF default capabilities:
Always CEF switching:               no
Always dCEF switching:              no
Default CEF switching:              yes
Default dCEF switching:             no
Drop multicast packets:             no
OK to punt packets:                 yes
NVGEN CEF state:                    no
fastsend() used:                    yes
CEF NSF capable:                    no
RPR+/SSO standby capable:           no
IPC delayed func on SSO:            no
FIB auto repair supported:          yes
LCs not running at init time:       no
Hardware forwarding supported:      no
Hardware forwarding in use:         no
Load-sharing pr. packet supported:  yes

Router# show cef state
CEF Status:
RP instance
common CEF enabled
IPv4 CEF Status:
CEF enabled/running
dCEF disabled/not running
CEF switching enabled/running
universal per-destination load sharing algorithm, id A189DD49
IPv6 CEF Status:
CEF enabled/running
dCEF disabled/not running
original per-destination load sharing algorithm, id A189DD49
Router# show cef state capabilities
CEF Capabilities:
Supported address families:         IPv4 IPv6
Active address families:            IPv4 IPv6
Distributed Platform:               no
Warm or Hot Standby supported:      no
CEF NSF capable:                    no
IPC delayed func on SSO:            no
Hardware forwarding:                no
Checker auto-repair supported:      yes
Crashdump on memory failure:        no
Support load-sharing alg config:    yes
Blocking STANDBY_HOT until synced:  no
IPv4 CEF Capabilities:
Default CEF switching:              yes
Always FIB switching:               no
Default dCEF switching:             no
Always dCEF switching:              no
Drop multicast packets:             no
OK to punt packets:                 yes
NVGEN CEF state:                    yes
fastsend() used:                    yes
Support per packet load sharing:    yes
Support L4 ports in load sharing:   yes
Multicast (*,G) groups in CEF:      no
Install local entries from RIB:     no

IPv6 CEF Capabilities:[1]
Default CEF switching:              yes
Always FIB switching:               no
Default dCEF switching:             no
Always dFIB switching:              no
Drop multicast packets:             no
OK to punt packets:                 yes
NVGEN CEF state:                    yes
fastsend() used:                    yes
L4 ports in load balancing support: yes

[1] This is the continuation of the output of the show cef state capabilities command.

show cef timers

This feature provides the following change to the output of the show cef timerscommand:

- The command output has been updated to reflect the new timers.

The table below compares the show cef timerscommand output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show cef timersCommand Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show cef timers
CEF background process
Expiration    Type
|        0.740  (parent)
|        0.740  ARP throttle
|        0.908  adjacency update hwidb
|        0.908  slow resolution
|        8.572  <unknown:6240E510/0>
CEF FIB scanner process
Expiration    Type
|        5.764  (parent)
|        5.764  checker scan-rib
|        6.340  checker scan-sw-hw
|       49.588  checker scan-hw-sw

Router# show cef timers
CEF background process
Expiration    Type
|       13.248  (parent)
|       13.248  FIB checkers: IPv4 scan-rib-ios scanner
|       13.248  FIB checkers: IPv4 scan-ios-rib scanner
|       13.248  FIB checkers: IPv6 scan-ios-rib scanner
Platform counter polling is not enabled
IPv4 CEF background process
Expiration    Type
|        0.600  (parent)
|        0.600  ARP throttle
|        0.600  adjacency update hwidb

show ip cef epoch

This feature provides the following change to the output of the show ip cef epochcommand:

The table below compares the show ip cef epochcommand output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show ip cef epochCommand Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show ip cef epoch
CEF epoch information:
Table: Default
Table epoch: 0 (33 entries at this epoch)
Adjacency table

Table epoch: 0 (7 entries at this epoch)

Router# show ip cef epoch
Table: Default
Database epoch: 0 (24 entries at this epoch)

show ipv6 cef epoch

This feature provides the following change to the output of the show ipv6 cef epochcommand:

The table below compares the show ipv6 cef epochcommand output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show ipv6 cef epochCommand Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show ipv6 cef epoch
CEF epoch information:
Table: Default
Table epoch: 1 (2 entries at this epoch)
Adjacency table
Table epoch: 0 (1 entries at this epoch)

Router# show ipv6 cef epoch
Table: Default
Database epoch: 1 (2 entries at this epoch)

show ip cef unresolved detail

This feature provides the following changes to the output of the show ip cef unresolved detailcommand:

- The new command output lists only unresolved prefixes.

- IPv4 and IPv6 are now separately addressed.

- Figures related to adjacencies are moved to the show adjacency summarycommand (see the show adjacency summary).

- Mtrie data structure descriptions are moved to a new command, the show ip cef treecommand (see the New Commands for the CEF Feature).

- Nothing is displayed if no unresolved adjacencies exist.

The table below compares the show ip cef unresolved detailcommand output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show ip cef unresolved detail Command Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show ip cef unresolved detail
IP CEF with switching (Table Version 59), flags=0x0
34 routes, 0 reresolve, 0 unresolved (0 old, 0 new), peak 2
34 leaves, 22 nodes, 27640 bytes, 80 inserts, 46 invalidations
0 load sharing elements, 0 bytes, 0 references
universal per-destination load sharing algorithm, id DF940F94
3(0) CEF resets, 0 revisions of existing leaves
Resolution Timer: Exponential (currently 1s, peak 1s)
0 in-place/0 aborted modifications
refcounts:  5933 leaf, 5888 node
Table epoch: 0 (34 entries at this epoch)
Adjacency Table has 7 adjacencies
4 IPv4 adjacencies
3 IPv6 adjacencies

Router# show ip cef unresolved detail
IPv4 CEF is enabled and running
VRF Default
25 prefixes (25/0 fwd/non-fwd)
Table id 0x0
Database epoch:        0 (25 entries at this epoch)
101.1.1.1/32, epoch 0, flags rib only nolabel, rib defined all labels
recursive via 102.2.2.2, unresolved

show ipv6 cef unresolved detail

This feature provides the following changes to the output of the show ipv6 cef unresolved detailcommand:

- Figures related to adjacencies are moved to the show adjacency summarycommand (see the show adjacency summary).

- Nothing is displayed in the output if there are no unresolved adjacencies.

The table below compares the show ipv6 cef unresolved detailcommand output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show ipv6 cef unresolved detail Command Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show ipv6 cef unresolved detail
IPv6 CEF is enabled and running
Slow processing intvl = 1 seconds backoff level current/max 0/0
0 unresolved prefixes, 0 requiring adjacency update
IPv6 CEF default table
20 prefixes

Router# show ipv6 cef unresolved detail
IPv6 CEF is enabled and running centrally.
VRF Default
6 prefixes (6/0 fwd/non-fwd)
Table id 0x1E000000
Database epoch:        0 (6 entries at this epoch)
2002::/128, epoch 0, flags rib only nolabel, rib defined all labels
recursive via 2003::BEEF, unresolved

show ipv6 cef non-recursive

This feature provides the following change to the output of the show ipv6 cef non-recursivecommand:

- The path information is changed to be more consistent with IPv4 path information.

The table below compares the show ipv6 cef non-recursivecommand output before ("Old" heading) and after ("New" heading) the Cisco Express Forwarding enhancements.

show ipv6 cef non-recursive Command Output Before and After Cisco Express Forwarding Enhancements

Old

New

Router# show ipv6 cef non-recursive
2001:1:12::/64
nexthop FE80::2D0:1FF:FEE4:6800 FastEthernet0/1
2001:2:13::/64
nexthop FE80::2D0:1FF:FEE4:6800 FastEthernet0/1
2001:2:22::/64
nexthop FE80::2D0:1FF:FEE4:6800 FastEthernet0/1

Router# show ipv6 cef non-recursive
::/0
no route
::/127
discard
2003::/128
nexthop 3003::DEAD Ethernet2/0
FE80::/10
receive for Null0
FF00::/8
multicast

New Commands for the CEF Feature

This section does not contain all new Cisco Express Forwarding commands. It contains only new commands introduced with the Cisco Express Forwarding enhancements to provide the same level of information that was available with the use of other commands before the Cisco Express Forwarding enhancements were implemented. Sample output is provided for the following new commands:

- show adjacency link

- show adjacency

- show adjacency detail

- show cef tree

- test cef table consistency detail

- show adjacency link

- show adjacency

- show adjacency detail

- show cef tree

- test cef table consistency detail

show adjacency link

The show adjacency link ipv4command and the show adjacency link ipv6command display information about IPv4 and IPv6 traffic, respectively, in the Cisco Express Forwarding adjacency table or the hardware Layer 3-switching adjacency table.

Per-protocol and interface summary adjacency information was moved from the show adjacency summary command to the show adjacency link command.

Following is sample output of the show adjacency link ipv4 command.

Router# show adjacency link ipv4
Protocol Interface                 Address
IP       FastEthernet0/0           10.60.17.2(6)
IP       FastEthernet0/0           10.60.17.20(6)
IP       FastEthernet0/0           10.60.17.254(7)
IP       FastEthernet0/1           172.17.22.1(16)

Following is sample output of the show adjacency link ipv6 command.

Router# show adjacency link ipv6
Protocol Interface                 Address
IPV6     FastEthernet0/1           2001:2:22::1(6)
IPV6     FastEthernet0/1           2001:2:22::2(3) (incomplete)
IPV6     FastEthernet0/1           FE80::2D0:1FF:FEE4:6800(14)
IPV6     Serial3/0                 point2point(7)
IPV6     Serial3/1                 point2point(10

show adjacency

The show adjacency prefix command shows adjacency information for the specified prefix.

Following are sample outputs from the show adjacency prefix command for an IPv4 prefix and an IPv6 prefix:

Router# show adjacency 172.17.22.1/24
Protocol Interface                 Address
IP       FastEthernet0/1           172.17.22.1(16)
Router# show adjacency 2001:2:22::1/64

Protocol Interface                 Address
IPV6     FastEthernet0/1           2001:2:22::1(6)

show adjacency detail

The show adjacency prefix detail command provides additional adjacency information for a specified prefix.

Information about the adjacency epoch was removed from the show ip cef epoch and show ipv6 cef epoch commands and is available from the show adjacency prefix detail command.

Following are sample outputs from the show adjacency prefix detail command for an IPv4 prefix and an IPv6 prefix:

Router# show adjacency 172.17.22.1/24 detail

Protocol Interface                 Address
IP       FastEthernet0/1           172.17.22.1(16)
0 packets, 0 bytes
epoch 0
sourced in sev-epoch 3
Encap length 14
00D001E4680000055FAF2C060800
ARP
Router# show adjacency 2001:2:22::1/64 detail

Protocol Interface                 Address
IPV6     FastEthernet0/1           2001:2:22::1(6)
0 packets, 0 bytes
epoch 0
sourced in sev-epoch 3
Encap length 14
00D001E4680000055FAF2C0686DD
IPv6 ND

show cef tree

The show{ip| ipv6} cef treecommand displays summary information about the underlying data structures representing the specified FIB tree.

Mtrie data structure information was removed from several commands for the implementation of the Cisco Express Forwarding enhancements. This command provides the Mtrie information removed from the show ip cef summary, show ip cef internal, and show ip cef detail commands.

Following is sample output for the show ip cef tree command:

Router# show ip cef tree
VRF Default tree information:
MTRIE/RTREE storing IPv4 addresses
24 entries (24/0 fwd/non-fwd)
Forwarding tree:
Forwarding lookup routine: IPv4 mtrie 8-8-8-8 optimized
33 inserts, 9 deletes
8-8-8-8 stride pattern
short mask protection enabled for <= 4 bits without process suspension
24 leaves (672 bytes), 22 nodes (22880 bytes)
25208 total bytes
leaf ops: 33 inserts, 9 deletes
leaf ops with short mask protection: 2 inserts, 1 delete
per-prefix length stats: lookup off, insert off, delete off
refcounts: 1356 leaf, 1324 node
node pools:
pool[C/8 bits]: 22 allocated (0 failed), 22880 bytes
Non-Forwarding tree:
38 inserts, 38 deletes
0 leaves (0 bytes), 0 nodes (0 bytes)
0 total bytes

test cef table consistency detail

The test cef table consistency detail command displays recorded Cisco Express Forwarding consistency records found by the following detection mechanisms: lc-detect, scan-rib-ios, scan-ios-rib, scan-lc-rp, and scan-rp-lc. The scan-lc-rp and scan-rp-lc detection mechanisms are available only on routers with line cards. You can configure the Cisco Express Forwarding prefix consistency-detection mechanisms using the cef table consistency-check command.

This command provides output that replaces the output provided by the removed and obsolete show ip cef inconsistency records, show ip cef inconsistency now, and show ip cef inconsistency now detailcommands.

Following is sample output for the test cef table consistency detailcommand:

Router# test cef table consistency detail

full-scan-rib-ios: Checking IPv4 RIB to FIB consistency
full-scan-rib-ios: FIB checked 12 prefixes, and found 0 missing.
full-scan-ios-rib: Checking IPv4 FIB to RIB consistency
full-scan-ios-rib: Checked 12 FIB prefixes in 1 pass, and found 0 extra.
full-scan-rp-lc: Sent 26 IPv4 prefixes to linecards in 1 pass
full-scan-rp-lc: Initiated IPv4 FIB check on linecards..4..1..0..
full-scan-rp-lc: FIB IPv4 check completed on linecards..1..0..4..
full-scan-rp-lc: Linecard 4 checked 26 IPv4 prefixes (ignored 0). 0 inconsistent.
full-scan-rp-lc: Linecard 1 checked 26 IPv4 prefixes (ignored 0). 0 inconsistent.
full-scan-rp-lc: Linecard 0 checked 26 IPv4 prefixes (ignored 0). 0 inconsistent.
full-scan-rib-ios: Checking IPv6 RIB to FIB consistency
full-scan-rib-ios: FIB checked 16 prefixes, and found 5 missing.
full-scan-ios-rib: Checking IPv6 FIB to RIB consistency
full-scan-ios-rib: Checked 11 FIB prefixes in 1 pass, and found 0 extra.
full-scan-rp-lc: Sent 11 IPv6 prefixes to linecards in 1 pass
full-scan-rp-lc: Initiated IPv6 FIB check on linecards..4..1..0..
full-scan-rp-lc: FIB IPv6 check completed on linecards..1..4..0..
full-scan-rp-lc: Linecard 4 checked 11 IPv6 prefixes (ignored 0). 0 inconsistent.
full-scan-rp-lc: Linecard 1 checked 11 IPv6 prefixes (ignored 0). 0 inconsistent.
full-scan-rp-lc: Linecard 0 checked 11 IPv6 prefixes (ignored 0). 0 inconsistent.
No IPv4 inconsistencies found, check took 00:00:01.444
Warning: 5 IPv6 inconsistencies found, check took 00:00:01.240

Unchanged CEF show Commands

Some Cisco Express Forwarding show commands related to the Cisco Express Forwarding enhancements were not changed with the introduction of the enhancements. The output of the following commands was not changed:

- show cef idb

- show cef interface

- show ip cef

- show ip cef non-recursive

- show ipv6 cef

- show ipv6 cef adjacency

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

Description of Cisco Express Forwarding commands

Cisco IOS IP Switching Command Reference

Description of Cisco Express Forwarding IPv6 commands

Cisco IOS IPv6 Command Reference

Information on MFI enhancements

MPLS Infrastructure Changes: Introduction of MFI and Removal of MPLS LSC and LC-ATM Features

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

Click Here

Feature Information for CEF Enhancements

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.

Feature Information for Cisco Express Forwarding

Feature Name

Releases

Feature Information

Cisco Express Forwarding Enhancements: Introduction of CLI Changes and Removal of IPv4 Fast Switching

12.4(20)T

The purpose of this document is to describe the changes based on the Cisco Express Forwarding infrastructure scalability enhancements that have been implemented to adapt to the evolution of the Internet and to support new platforms and features. The changes are the removal of IP fast switching and the introduction of command line interface (CLI) modifications.

This document lists Cisco Express Forwarding CLI commands that are removed, replaced, changed, and new. To help you transition to the new CLI format, the document illustrates the output for new commands and changed commands.

Enhancements to Cisco Express Forwarding enable it to operate with the Multiprotocol Label Switching (MPLS) Forwarding Infrastructure (MFI) and guarantee consistency across Cisco IOS release trains. Cisco Express Forwarding infrastructure changes were introduced and implemented in the Cisco IOS 12.2(25)S-based releases and were added for T releases in Cisco IOS Release 12.4(20)T.

Cisco Express Forwarding is an advanced Layer 3 IP switching technology. It optimizes network performance and scalability for all kinds of networks: those that carry small amounts of traffic and those that carry large amounts of traffic in complex patterns, such as the Internet, and networks characterized by intensive web-based applications or interactive sessions.

In Cisco IOS Release 12.4(20)T, this feature was introduced.

Glossary

adjacency --A relationship formed between selected neighboring routers and end nodes for the purpose of exchanging routing information. Adjacency is based upon the use of a common media segment by the routers and nodes involved.

Cisco Express Forwarding --A Layer 3 switching technology. Cisco Express Forwarding can also refer to central Cisco Express Forwarding mode, one of two modes of Cisco Express Forwarding operation. Cisco Express Forwarding enables a Route Processor (RP) to perform express forwarding. Distributed Cisco Express Forwarding is the other mode of Cisco Express Forwarding operation.

distributed Cisco Express Forwarding --A type of Cisco Express Forwarding switching in which line cards (such as Versatile Interface Processor (VIP) line cards) maintain identical copies of the forwarding information base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters; this relieves the Route Switch Processor of involvement in the switching operation.

FIB --forwarding information base. A component of Cisco Express Forwarding. The router uses the FIB lookup table to make destination-based switching decisions during Cisco Express Forwarding operation. The router maintains a mirror image of the forwarding information in an IP routing table.

IDB --Interface Descriptor Block. An IDB is a special control structure internal to the Cisco IOS software that contains information such as the IP address, interface state, and packet statistics. Cisco IOS software maintains one IDB for each interface present on a platform and one IDB for each subinterface.

IPRM --IP Rewrite Manager. The IPRM is a module that manages the interaction between Cisco Express Forwarding, the IP Label Distributions Modules (LDM), and the Multiprotocol Label Switching (MPLS) Forwarding Infrastructure (MFI).

Mtrie --multiway tree. The Mtrie is a data structure in which routes are stored. The Mtrie is part of the IP lookup algorithm used in Cisco Express Forwarding.

prefix --The network address portion of an IP address. A prefix is specified by a network and mask and is generally represented in the format network/mask. The mask indicates which bits are the network bits. For example, 10.0.0.0/16 means that the first 16 bits of the IP address are masked, making them the network bits. The remaining bits are the host bits. In this example, the network number is 10.0.

RIB --Routing Information Base. A central repository of routes that contains Layer 3 reachability information and destination IP addresses or prefixes. The RIB is also known as the routing table.

RP --Route Processor. The processor module in the Cisco 7000 series routers that contains the CPU, system software, and most of the memory components that are used in the router. It is sometimes called a supervisory processor.

VRF --A Virtual Private Network (VPN) routing/forwarding instance. A VRF consists of an IP routing table, a derived forwarding table, a set of interfaces that use the forwarding table, and a set of rules and routing protocols that determine what goes into the forwarding table. In general, a VRF includes the routing information that defines a customer VPN site that is attached to a provider edge (PE) router.

Chapter 13. IPv6 CEF-Switched Tunnels

Cisco Express Forwarding switching can be used for IPv6 manually configured tunnels.

- Finding Feature Information

- Information About IPv6 CEF-Switched Tunnels

- Additional References

- Feature Information for IPv6 CEF-Switched Tunnels

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to Click Here . An account on Cisco.com is not required.

Information About IPv6 CEF-Switched Tunnels

- IPv6 Manually Configured Tunnels

IPv6 Manually Configured Tunnels

A manually configured tunnel is equivalent to a permanent link between two IPv6 domains over an IPv4 backbone. The primary use is for stable connections that require regular secure communication between two edge devices or between an end system and an edge device, or for connection to remote IPv6 networks.

An IPv6 address is manually configured on a tunnel interface, and manually configured IPv4 addresses are assigned to the tunnel source and the tunnel destination. The host or device at each end of a configured tunnel must support both the IPv4 and IPv6 protocol stacks. Manually configured tunnels can be configured between border devices or between a border device and a host. Cisco Express Forwarding switching can be used for IPv6 manually configured tunnels, or Cisco Express Forwarding switching can be disabled if process switching is needed.

Additional References

Related Documents

Related Topic

Document Title

IPv6 addressing and connectivity

IPv6 Configuration Guide

Tunnels

Interface and Hardware Component Configuration Guide

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

IPv6 commands

Cisco IOS IPv6 Command Reference

Cisco IOS IPv6 features

Cisco IOS IPv6 Feature Mapping

Standards and RFCs

Standard/RFC

Title

RFCs for IPv6

IPv6 RFCs

MIBs

MIB

MIBs Link

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

Click Here

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

Click Here

Feature Information for IPv6 CEF-Switched Tunnels

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.

Feature Information for IPv6 CEF-Switched Tunnels

Feature Name

Releases

Feature Information

CEFv6 Switching for 6to4 Tunnels

12.2(28)SB

12.2(25)SG

12.2(33)SRA

12.2(18)SXE

12.2(12)T

12.4

15.0(1)S

Cisco IOS XE 3.9(S)

Cisco Express Forwarding switching can be used for IPv6 manually configured tunnels.

IPv6 Switching: CEFv6 Switched Automatic IPv4-Compatible Tunnels

12.2(2)T

12.2(52)SG

12.2(33)SRA

12.2(17a)SX1

Cisco IOS XE 3.9(S)

IPv6 supports this feature.

IPv6 Switching: CEFv6 Switched Configured IPv6 over IPv4 Tunnels

12.2(13)T

12.2(52)SG

12.2(33)SRA

12.2(17a)SX1

Cisco IOS XE 3.9(S)

IPv6 supports this feature.

IPv6 Switching: CEFv6 Switched ISATAP Tunnels

12.2(15)T

12.2(25)SG

3.2.0SG

15.0(2)SG

12.2(33)SRA

12.2(17a)SX1

Cisco IOS XE 3.9(S)

IPv6 supports this feature.