Networking Software (IOS & NX-OS)

Table Of Contents

Configuring BGP Consistency Checker

Finding Feature Information

Contents

Information About BGP Consistency Checker

BGP Consistency Checker

How to Configure BGP Consistency Checker

Configure BGP Consistency Checker

Configuration Examples for BGP Consistency Checker

Example: Configuring BGP Consistency Checker

Additional References

Related Documents

MIBs

Technical Assistance

Feature Information for BGP Consistency Checker

Configuring BGP Consistency Checker

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First Published: March 18, 2011

Last Updated: March 30, 2011

The BGP Consistency Checker feature provides a way to identify certain types of BGP route inconsistencies with peers: next-hop label inconsistency, RIB-out inconsistency, and aggregation inconsistency. Upon finding such an inconsistency, the system sends a syslog error message and takes appropriate action if configured to do so.

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 BGP Consistency Checker" section.

Use Cisco Feature Navigator to find information about platform support and Cisco 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

•Information About BGP Consistency Checker

•How to Configure BGP Consistency Checker

•Configuration Examples for BGP Consistency Checker

•Additional References

•Feature Information for BGP Consistency Checker

Information About BGP Consistency Checker

•BGP Consistency Checker

BGP Consistency Checker

A BGP route inconsistency with a peer occurs when an update or a withdraw is not sent to a peer, and black-hole routing can result. To identify that issue, BGP consistency checker was created as a low-priority process that does nexthop-label, RIB-out, and aggregation consistency checks at a configurable interval. When enabled, BGP consistency checker is performed for all address families. Configuring BGP consistency checker is recommended.

Once the process identifies such an inconsistency, it will report the inconsistency with a syslog message and optionally take action if the auto-repair keyword is specified. The action taken depends on the type of inconsistency found.

•Next-Hop Label Consistency Check—When two paths have the same next hop because they are advertised by the same provider edge router (PE), they should also have the same next-hop label. If the labels are different, there is an inconsistency. If the auto-repair keyword is specified, the system will send a route-refresh request.

•RIB-Out Consistency Check—If a network passes an outbound policy and is not sent, or if a network does not pass an outbound policy and is sent, there is an inconsistency. If the auto-repair keyword is specified, the system will send a route-refresh request.

•Aggregation Consistency Check—If specific routes and the aggregated route become out of sync, an inconsistency can occur. Either the error-message keyword or the auto-repair keyword will trigger aggregation reevaluation.

In the unlikely event that you receive a syslog message about an inconsistency, notify your Cisco technical support representative with the syslog message exactly as it appears. The following are examples of such syslog messages:

•"Net 10.0.0.0/32 has Nexthop-Label inconsistency."

•"Net 10.0.0.0/32 in IPv4 Unicast has rib-out inconsistency for update-group 4 - outbound-policy fails."

How to Configure BGP Consistency Checker

•Configure BGP Consistency Checker (required)

Configure BGP Consistency Checker

SUMMARY STEPS

1. enable

2. configure terminal

3. router bgp autonomous-system-number

4. bgp consistency-checker {error-message | auto-repair} [interval minutes]

5. end

6. show ip bgp [vpnv4 | vpnv6] all inconsistency nexthop-label

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	router bgp autonomous-system-number Example: Router(config)# router bgp 500	Configures a BGP routing process.
Step 4	bgp consistency-checker {error-message | auto-repair} [interval minutes] Example: Router(config-router)# bgp consistency-checker auto-repair interval 720	Enables BGP consistency checker. •The default interval is 1440 minutes (one day). The range is 5 to 1440 minutes.
Step 5	end Example: Router(config-router)# end	Ends the current configuration and returns to privileged EXEC mode.
Step 6	show ip bgp [vpnv4 | vpnv6] all inconsistency nexthop-label Example: Router# show ip bgp all inconsistency nexthop-label	(Optional) Displays routes that have a nexthop-label inconsistency found. •This step is not part of configuring the feature; it is provided in case you receive a syslog message about a nexthop-label inconsistency and you want to display those routes.

Configuration Examples for BGP Consistency Checker

•Example: Configuring BGP Consistency Checker

Example: Configuring BGP Consistency Checker

The following example configures BGP consistency checker with auto-repair at the default interval of one day:

router bgp 65000

 bgp consistency-checker auto-repair

Additional References

Related Documents

Related Topic	Document Title
Cisco IOS commands	Cisco IOS Master Commands List, All Releases
BGP commands	Cisco IOS IP Routing: BGP Command Reference
BGP configuration tasks	Cisco IOS IP Routing: BGP Configuration Guide

MIBs

MIB	MIBs Link
•—	To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL: http://www.cisco.com/go/mibs

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.	http://www.cisco.com/cisco/web/support/index.html

Feature Information for BGP Consistency Checker

Table 1 lists the release history for this feature.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

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Note Table 1 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.

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Table 1 Feature Information for BGP Consistency Checker 

Feature Name	Releases	Feature Information
BGP Consistency Checker	15.1(2)S	The BGP Consistency Checker feature provides a way to identify three types of BGP route inconsistencies with peers: next-hop label inconsistency, RIB-out inconsistency, and aggregation inconsistency. Upon finding such inconsistency, the system sends a syslog error message and takes appropriate action if configured to do so. The following command was introduced: bgp consistency-checker The following command was modified: show ip bgp vpnv4.

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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.

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