Table Of Contents
Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
Prerequisites for Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
Restrictions for Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
Information About Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
NetFlow BGP Next Hop Support Benefits
NetFlow BGP Next Hop Support and NetFlow Aggregation
How to Configure NetFlow BGP Next Hop Support for Accounting and Analysis
Configuring NetFlow BGP Next Hop Accounting
Configuration Examples for NetFlow BGP Next Hop Support for Accounting and Analysis
Configuring NetFlow BGP Next Hop Accounting: Examples
Feature Information for Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
First Published: June 19, 2006Last Updated: June 19, 2006This document provides information about and instructions for configuring NetFlow Border Gateway Protocol (BGP) next hop support. This feature lets you measure network traffic on a per BGP next hop basis.
NetFlow is a Cisco IOS application that provides statistics on packets flowing through the router. It is emerging as a primary network accounting and security technology.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see 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 for Configuring NetFlow BGP Next Hop Support for Accounting and Analysis" section.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Contents
This document includes the following sections:
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Prerequisites for Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
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Prerequisites for Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
Before you can configure the NetFlow BGP Next Hop Support feature, you must:
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Restrictions for Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
Cisco IOS Releases 12.2(14)S, 12.0(22)S, or 12.2(15)T
If your router is running a version of Cisco IOS prior to releases 12.2(14)S, 12.0(22)S, or 12.2(15)T the ip route-cache flow command is used to enable NetFlow on an interface.
If your router is running Cisco IOS release 12.2(14)S, 12.0(22)S, 12.2(15)T, or later the ip flow ingress command is used to enable NetFlow on an interface.
Recursive Load Sharing
The NetFlow cache does not capture the BGP next hop when the route to that BGP next hop is recursively load-shared via several IGP links. Instead, the NetFlow cache captures (as the BGP next hop) the effective simple next hop from among a random selection of the load-shared routes to which the BGP route recurses.
Memory Impact
For BGP-controlled routes, the NetFlow BGP Next Hop Support feature adds 16 bytes to each NetFlow flow record. This increases memory requirements by 16 bytes times the number of flow cache entries that have BGP-controlled prefixes.
Performance Impact
Because the BGP next hop is fetched from the CEF path only once per flow, the performance impact of the NetFlow BGP Next Hop Support feature is minimal.
Information About Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
To configure the NetFlow BGP Next Hop Support feature, you must understand the following concepts:
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NetFlow BGP Next Hop Support Benefits
Without the NetFlow BGP Next Hop Support feature, NetFlow exports only IP next hop information (which provides information for only the next router). This feature adds BGP next hop information to the data export.
The NetFlow BGP Next Hop Support feature lets you find out through which service provider the traffic is going. This functionality is useful if you have arrangements with several other service providers for fault-protected delivery of traffic. The feature lets you charge customers more per packet when traffic has a more costly destination—you can pass on some of the cost associated with expensive trans-oceanic links or charge more when traffic is sent to another ISP with which you have an expensive charge agreement.
This feature requires the NetFlow Version 9 export format for its data export.
NetFlow BGP Next Hop Support and NetFlow Aggregation
The Cisco IOS NetFlow Aggregation feature summarizes NetFlow export data on a router before the data is exported to the NetFlow Collection Engine (formerly called the NetFlow FlowCollector). The NetFlow BGP Next Hop Support feature provides the BGP next hop and its related aggregation scheme and provides BGP next hop information within each NetFlow record.
How to Configure NetFlow BGP Next Hop Support for Accounting and Analysis
See the following sections for configuration tasks for the NetFlow BGP Next Hop Support feature. Each task in the list is identified as either required or optional.
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Configuring NetFlow BGP Next Hop Accounting
Perform the steps in this required task to configure NetFlow BGP next hop accounting.
This section shows how to configure NetFlow BGP next hop accounting for the main cache and aggregation caches. You can enable the export of origin AS information or peer AS information, but not both.
SUMMARY STEPS
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DETAILED STEPS
Troubleshooting Tips
If there are no BGP-specific flow records in the NetFlow cache, make sure that CEF or dCEF switching is enabled and that the destination for NetFlow data export is configured. Also check the routing table for BGP routes.
Verifying the Configuration
Perform the steps in this optional task to verify successful configuration of NetFlow BGP next hop accounting.
SUMMARY STEPS
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DETAILED STEPS
Step 1
Use this command to enable privileged EXEC mode. Enter your password if required. For example:
Router> enableRouter#Step 2
Use this command to verify successful configuration of NetFlow BGP next hop accounting. For example:
Router# show ip cache verbose flowIP packet size distribution (120 total packets):1-32 64 96 128 160 192 224 256 288 320 352 384 416 448 480.000 .000 .000 1.00 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000512 544 576 1024 1536 2048 2560 3072 3584 4096 4608.000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000IP Flow Switching Cache, 17826816 bytes8 active, 262136 inactive, 8 added26 ager polls, 0 flow alloc failuresActive flows timeout in 30 minutesInactive flows timeout in 15 secondsIP Sub Flow Cache, 1081480 bytes8 active, 65528 inactive, 8 added, 8 added to flow0 alloc failures, 0 force free1 chunk, 1 chunk addedlast clearing of statistics neverProtocol Total Flows Packets Bytes Packets Active(Sec) Idle(Sec)-------- Flows /Sec /Flow /Pkt /Sec /Flow /FlowSrcIf SrcIPaddress DstIf DstIPaddress Pr TOS Flgs PktsPort Msk AS Port Msk AS NextHop B/Pk ActiveMUL:M_Opaks M_Obytes BGP:BGP_NextHopEt0/0/2 12.0.0.2 Et0/0/4 13.0.0.5 01 00 10 200000 /8 0 0800 /8 0 11.0.0.6 100 0.0BGP:26.0.0.6Et0/0/2 12.0.0.2 Et0/0/4 15.0.0.7 01 00 10 200000 /8 0 0800 /8 0 11.0.0.6 100 0.0BGP:26.0.0.6Et0/0/2 12.0.0.2 Et0/0/4 15.0.0.7 01 00 10 200000 /8 0 0000 /8 0 11.0.0.6 100 0.0BGP:26.0.0.6This command displays a detailed summary of NetFlow statistics (including additional NetFlow fields in the header when NetFlow Version 9 data export is configured).
Step 3
Use this command to verify the configuration of a BGP next hop type of service (ToS) aggregation cache. For example:
Router# show ip cache flow aggregation bgp-nexthop-tosIP Flow Switching Cache, 278544 bytes1 active, 4095 inactive, 1 added8 ager polls, 0 flow alloc failuresActive flows timeout in 30 minutesInactive flows timeout in 15 secondsIP Sub Flow Cache, 17224 bytes1 active, 1023 inactive, 1 added, 1 added to flow0 alloc failures, 0 force free1 chunk, 1 chunk addedSrc If Src AS Dst If Dst AS TOS Flows Pkts B/PkActiveBGP NextHopEt0/0/2 0 Et0/0/4 0 00 9 36 408.2BGP:26.0.0.6Step 4
Use this command to exit to user EXEC mode. For example:
Router# exitRouter>
Configuration Examples for NetFlow BGP Next Hop Support for Accounting and Analysis
This section provides the following configuration example: Configuring NetFlow BGP Next Hop Accounting: Examples
Configuring NetFlow BGP Next Hop Accounting: Examples
The following example shows how to configure NetFlow BGP next hop accounting with origin AS and BGP next hop statistics for the main cache:
configure terminal!ip flow-export version 9 origin-as bgp-nexthopip flow-export destination 172.16.10.2 991!interface ethernet 0/0ip flow ingress!endThe following example shows how to configure a NetFlow BGP next hop ToS aggregation cache scheme:
configure terminal
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ip flow-aggregation cache bgp-nexthop-tosexport destination 172.16.10.2 991enabled!interface ethernet 0/0ip flow ingress!endAdditional References
For additional information related to NetFlow BGP next hop support for accounting and analysis, see the following references.
Related Documents
Overview of Cisco IOS NetFlow
List of the features documented in the Cisco IOS NetFlow Configuration Guide configuration guide
The minimum information about and tasks required for configuring NetFlow and NetFlow Data Export
Getting Started with Configuring NetFlow and NetFlow Data Export
Tasks for configuring NetFlow to capture and export network traffic data
Tasks for configuring Configuring MPLS Aware NetFlow
Tasks for configuring MPLS egress NetFlow accounting
Tasks for configuring NetFlow input filters
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
Tasks for configuring Random Sampled NetFlow
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
Tasks for configuring NetFlow aggregation caches
Tasks for configuring NetFlow multicast support
Tasks for detecting and analyzing network threats with NetFlow
Tasks for configuring NetFlow Reliable Export With SCTP
Tasks for configuring NetFlow Layer 2 and Security Monitoring Exports
Tasks for configuring the SNMP NetFlow MIB
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
Tasks for configuring the NetFlow MIB and Top Talkers feature
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Information for installing, starting, and configuring the CNS NetFlow Collection Engine
Standards
MIBs
RFCs
Technical Assistance
Feature Information for Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
Table 1 lists the features in this module and provides links to specific configuration information. Only features that were introduced or modified in Cisco IOS Release 12.2(1) or 12.0(3)S or a later release appear in the table.
Not all commands may be available in your Cisco IOS software release. For details on when support for a specific command was introduced, see the command reference documentation.
For information on a feature in this technology that is not documented here, see the "Cisco IOS NetFlow Features Roadmap" module.
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform. Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.
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Table 1 Feature Information for Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
NetFlow BGP Next Hop Support
12.3(1), 12.2(18)S, 12.0(26)S, 12.2(27)SBC
The NetFlow Border Gateway Protocol (BGP) Next Hop Support feature lets you measure network traffic on a per BGP next hop basis. Without the NetFlow BGP Next Hop Support feature, NetFlow exports only IP next hop information (which provides only the address of the next router); this feature adds BGP next hop information to the data export.
The following sections provide information about this feature:
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The following commands were modified by this feature: ip flow-aggregation cache, ip flow-export, show ip cache flow aggregation, and show ip cache verbose flow.
Glossary
BGP—Border Gateway Protocol. Interdomain routing protocol that replaces Exterior Gateway Protocol (EGP). BGP exchanges reachability information with other BGP systems. It is defined by RFC 1163.
BGP next hop—IP address of the next hop to be used to reach a specific destination.
CEF—Cisco Express Forwarding. A Layer 3 IP switching technology that optimizes network performance and scalability for networks with large and dynamic traffic patterns.
dCEF—distributed Cisco Express Forwarding. A type of CEF 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.
fast switching—Cisco feature in which a route cache expedites packet switching through a router.
FIB—forwarding information base. A table containing the information needed to forward IP datagrams. At a minimum, this table contains the interface identifier and next hop information for each reachable destination network prefix. The FIB is distinct from the routing table (also called the routing information base), which holds all routing information received from routing peers.
flow—(NetFlow) A set of packets with the same source IP address, destination IP address, source and destination ports, and type of service, and the same interface on which flow is monitored. Ingress flows are associated with the input interface, and egress flows are associated with the output interface.
NetFlow—A Cisco IOS application that provides statistics on packets flowing through the router. It is emerging as a primary network accounting and security technology.
NetFlow Aggregation—A NetFlow feature that lets you summarize NetFlow export data on an IOS router before the data is exported to a NetFlow data collection system such as the NetFlow Collection Engine. This feature lowers bandwidth requirements for NetFlow export data and reduces platform requirements for NetFlow data collection devices.
NetFlow Collection Engine (formerly NetFlow FlowCollector)—Cisco application that is used with NetFlow on Cisco routers and Catalyst series switches. The NetFlow Collection Engine collects packets from the router that is running NetFlow and decodes, aggregates, and stores them. You can generate reports on various aggregations that can be set up on the NetFlow Collection Engine.
NetFlow v9—NetFlow export format Version 9. A flexible and extensible means for carrying NetFlow records from a network node to a collector. NetFlow Version 9 has definable record types and is self-describing for easier NetFlow Collection Engine configuration.
ToS—type of service byte. Second byte in the IP header that indicates the desired quality of service for a particular datagram.
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