Cisco ASR 9000 Series Routing Configuration Guide

This does not affect the GSHUT community on a route that already had this community when it was
received; it only affects the GSHUT community when this router adds it.
Note
No Automatic Shutdown
The Graceful Maintenance feature does not perform any shutdown. When Graceful Maintenance is configured,
it remains configured, even through system restarts. It is intended to be used in conjunction with a shutdown
of a router or a BGP neighbor. The operator must explicitly shut down whenever it is needed. After Graceful
Maintenance is no longer required, the operator must explicitly deactivate it. Graceful Maintenance may be
deactivated either after the shutdown is completed, or after the deactivated facilities are again brought up.
Whether to leave Graceful Maintenance activated through a bring-up operation depends on whether the
transient routing during the bring-up operation is considered a problem.
When to Shut Down After Graceful Maintenance
The router or link can be shut down after the network has converged as a result of a graceful-maintenance
activation. Convergence can take from less than a second to more than an hour. Unfortunately, a single router
cannot know when a whole network has converged. After a graceful-maintenance activation, it can take a few
seconds to start sending updates. Then, the “InQ” and “OutQ” of neighbors in the show bgp <vrf> <afi> <safi>
summary command's output indicates the level of BGP messaging. Both InQ and OutQ should be 0 after
convergence. Neighbors should stop sending traffic. However, they won't stop sending traffic if they do not
have alternate paths; and in that case traffic loss cannot be prevented.
Activate Graceful Maintenance under BGP Router (All Neighbors)
Activating Graceful Maintenance under a BGP router results in activatebeing configured under
graceful-maintenance for all neighbors. With just this one configuration, you get the same result if you were
to go to every neighbor that has graceful-maintenance configured, and added activate under it. If you add
the keyword all-neighbors, thus, graceful-maintenance activate all-neighbors, then the router acts as if
you configured graceful-maintenance activate under every neighbor.
We suggest that you activate Graceful Maintenance under a BGP router instance only if it is acceptable
to send the GSHUT community for all routes on every neighbor. Re-sending all routes to every neighbor
can take significant amount of time on a large router. Sending GSHUT to a neighbor that does not have
alternative routes is pointless. If a router has many of such neighbors then a significant amount of time
can be saved by not activating Graceful Maintenance on them.
Note
The BGP Graceful Maintenance feature allows you to enable Graceful Maintenance either on a single neighbor,
on a group of neighbors across BGP sessions, or on all neighbors. Enabling Graceful Maintenance under a
neighbor sub-mode, does two things:
1
All routes that are advertised to this neighbor that has the graceful-shut attribute are advertised to that
neighbor with the GSHUT community.
2
Enters graceful-maintenance configuration mode to allow further configuration.
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.3.x
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Implementing BGP
BGP Graceful Maintenance

Cisco ASR 9000 Series Specifications

General

Brand	Cisco
Model	ASR 9000 Series
Category	Network Router
Language	English