Cisco ASR 9000 Series Routing Configuration Manual page 156

BGP Graceful Maintenance
Using the activate keyword under graceful-maintenance, causes the following:
1 All routes that are received from this neighbor acquire the graceful-shut attribute.
2 All routes that are advertised to this neighbor are re-advertised to that neighbor with the GSHUT community.
SUMMARY STEPS
1. configure
2. router bgp as-number
3. graceful-maintenance activate [ all-neighbors | retain-routes ]
4. commit
DETAILED STEPS
Command or Action
Step 1 configure
Step 2 router bgp as-number
Example:
RP/0/RSP0/CPU0:router(config)#
router bgp 120
Step 3 graceful-maintenance activate [
all-neighbors | retain-routes ]
Example:
RP/0/RSP0/CPU0:router(config-bgp)#
graceful-maintenance activate
all-neighhbors
Step 4 commit
What to Do Next
After activating Graceful Maintenance, you must wait for all the routes to be sent and for the neighboring
routers to redirect their traffic away from the router or link under maintenance. After the traffic is redirected,
then it is safe to take the router or link out of service. While there is no definitive way to know when all the
routes have been sent, you can use the show bgp summary command to check the OutQ of the neighbors.
When OutQ reaches a value 0, there are no more updates to be sent.
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.3.x
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Purpose
Specifies the BGP AS number and enters the BGP configuration mode,
allowing you to configure the BGP routing process.
Announces routes with the g-shut community and other attributes as configured
under the neighbors. This causes neighbors to reject routes from this router
and choose alternates. This allows the router to be gracefully brought in or out
of service. If you use the all-neighbors keyword, Graceful Maintenance is
activated even for those neighbors that do not have it activated. Choosing
retain-routes causes RIB to retain BGP routes when the BGP process is
stopped. Use the retain-routes option when only BGP must be brought down
instead of the entire router, and when it is known that neighboring routers are
kept in operation during the maintenance of the local BGP. If RIB has
alternative routes provided by another protocol or a default route, then it is
recommended that you do not to retain BGP routes after the BGP process
stops.
Implementing BGP