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.
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
www.cisco.com/go/cfn. 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 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 theshowipcefcommand. 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
If Cisco Express Forwarding is not enabled on your platform, the output for the showipcefcommand 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 ipcefdistributed 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:
Theipceftableevent-logcommand allows you to increase or decrease the number of entries that the event log can hold.
The clearipcefevent-log command allows you to clear all event log entries.
You can use the following commands to display Cisco Express Forwarding events:
Theshowipcefeventscommand displays all recorded Cisco Express Forwarding forwarding information base (FIB) and adjacency events.
The debugipcef command and the events keyword record general Cisco Express Forwarding events as they occur.
The debugipceftablecommand 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
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
No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.
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.
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
An account on Cisco.com is not required.
Table 1 Feature Information for Configuring the Display of Recorded Cisco Express Forwarding Events
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.
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.
CiscoExpressForwarding--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.
distributedCiscoExpressForwarding--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.
linecard--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, 126.96.36.199/16 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.