The BGP NSR Auto Sense feature is the default behavior implemented to reduce unnecessary churn in the event of a Route Processor
(RP) failover. Prior to this feature, when an Active RP went down, the new Active RP that was taking over to provide Border
Gateway Protocol (BGP) nonstop routing (NSR) would send a route-refresh request to all peers configured with NSR. However,
the new Active RP had already received all the incoming updates while acting as the Standby RP. Sending route-refresh requests
caused unnecessary BGP churn during switchover; this feature prevents such route-refresh requests by default. This feature
also provides NSR support to peers that lack route-refresh capability. If you want to revert to the old behavior of sending
route-refresh requests, a new command is available to make that happen.
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
www.cisco.com/go/cfn. An account on Cisco.com is not required.
Information About BGP NSR Auto Sense
Benefits of BGP NSR Auto Sense
The BGP NSR Auto Sense feature has the following benefits:
This feature is a default behavior that reduces unnecessary churn in the event of a Route Processor (RP) failover. Prior to
this feature, when an Active RP went down, the new Active RP that was taking over to provide BGP nonstop routing (NSR) would
send a route-refresh request to all peers configured with NSR. However, the Active RP had already received all the incoming
updates while acting as the Standby RP. Sending route-refresh requests caused unnecessary BGP churn during switchover; this
feature prevents such route-refresh requests by default.
This feature also provides NSR support to peers that lack route-refresh capability. Prior to this feature, NSR was not supported
for peers that lack route-refresh capability.
There is no need to configure this feature; it is the default behavior in releases where this feature is implemented.
If you want to revert to the former behavior of a new Active RP sending route-refresh requests when an RP goes down, you can
use the
bgp sso route-refresh-enable command.
Consequence of Reverting to NSR Without Auto Sense
You might have a reason not to want the default behavior of the BGP NSR Auto Sense feature. If you want to revert to the former
behavior of a new Active RP sending route-refresh requests when an RP goes down, you can use the
bgp sso route-refresh-enable command. This action causes peers that did not exchange route-refresh capability in the received OPEN message to have NSR
support disabled.
How to Disable the BGP NSR Auto Sense Feature
Disabling the BGP NSR Auto Sense Feature
The BGP NSR Auto Sense feature is enabled by default. Perform this task only if you want to disable the feature, for example,
if routes that were being advertised at the point of switchover did not get processed by the Standby RP (new Active RP) for
some reason. In that case, sending a route-refresh to request all the routes that the peer had ever advertised would be helpful.
After performing this task, in the event of a failover, a new Active RP will send route-refresh requests to peers configured
with NSR.
SUMMARY STEPS
enable
configure terminal
router bgp as-number
bgp sso route-refresh-enable
end
show ip bgp vpnv4 all neighbor [ip-address]
show ip bgp vpnv4 all sso summary
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 as-number
Example:
Router(config)# router bgp 6500
Configures a BGP routing process and enters router configuration mode.
The
as-number argument indicates the number of an autonomous system that identifies the router to other BGP routers and tags the routing
information passed along. Valid numbers are from 0 to 65535. Private autonomous system numbers that can be used in internal
networks range from 64512 to 65535.
Regarding the 4-byte AS configuration, please see the
bgp asnotation dot command in the
IP Routing: BGP Command Reference.
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.
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 www.cisco.com/go/cfn. An account on Cisco.com is not required.
Table 1. Feature Information for BGP NSR Auto Sense
Feature Name
Releases
Feature Information
BGP NSR Auto Sense
15.2(2)S
Cisco IOS XE Release 3.6S
The BGP NSR Auto Sense feature is implemented by default to reduce unnecessary churn in the event of an RP failover. This
feature also provides NSR support to peers that lack route-refresh support.
The following command was introduced:
bgp sso route-refresh-enable .
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