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The BGP Graceful Shutdown feature reduces or eliminates the loss of traffic along a link being shut down for maintenance. Routers always have a valid route available during the convergence process. This feature is used primarily for maintenance on a link between a Provider Edge (PE), PE-PE, PE- Route Reflector (RR), PE-Customer Edge (CE) and CE.
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.
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Information About BGP Graceful Shutdown
There are times when planned maintenance operations cause routing changes in BGP. After the shutdown of eBGP and iBGP peering sessions between autonomous system border routers (ASBRs), BGP devices are temporarily unreachable during BGP convergence. The goal of gracefully shutting down one or more BGP sessions is to minimize traffic loss during the planned shutdown and subsequent reestablishment of the sessions.
The BGP Graceful Shutdown feature reduces or eliminates the loss of inbound or outbound traffic flows that were initially forwarded along the peering link that is being shut down for maintenance. This feature is primarily for PE-CE, PE-RR and PE-PE links. Lowering the local preference for paths received over the session being shutdown renders the affected paths less preferred by the BGP decision process, but still allows the paths to be used during the convergence while alternative paths are propagated to the affected devices. Therefore, devices always have a valid route available during the convergence process.
The feature also allows vendors to provide a graceful shutdown mechanism that does not require any router reconfiguration at maintenance time. The benefits of the BGP Graceful Shutdown feature are fewer lost packets and less time spent reconfiguring devices.
The GSHUT community is a well-known community used in conjunction with the BGP Graceful Shutdown feature. The GSHUT community attribute is applied to a neighbor specified by the neighbor shutdown graceful command, thereby gracefully shutting down the link in an expected number of seconds. The GSHUT community is always sent by the GSHUT initiator.
The GSHUT community is specified in a community list, which is referenced by a route map and then used to make policy routing decisions.
The GSHUT community can also be used in the show ip bgp community command to limit output to GSHUT routes.
How to Configure BGP Graceful Shutdown
1.
enable
2.
configure
terminal
3.
router
bgp
autonomous-system-number
4.
neighbor
{ipv4-address
|
ipv6-address}
remote-as
number
5.
neighbor
{ipv4-address |
ipv6-address |
peer-group-name}
shutdown
graceful
seconds {community
value [local-preference
value] |
local-preference
value}
6.
end
7.
show
ip
bgp
community
gshut
Perform this task on a BGP peer to the device where you enabled the BGP Graceful Shutdown feature.
1.
enable
2.
configure
terminal
3.
router
bgp
autonomous-system-number
4.
neighbor
{ipv4-address |
ipv6-address}
remote-as
number
5.
neighbor
{ipv4-address |
ipv6-address}
activate
6.
neighbor
{ipv4-address |
ipv6-address}
send-community
7.
exit
8.
route-map
map-tag
[permit |
deny] [sequence-number]
9.
match community
{standard-list-number |
expanded-list-number |
community-list-name [exact]}
10.
exit
11.
ip community-list
{standard |
standard
list-name} {deny |
permit}
gshut
12.
router
bgp
autonomous-system-number
13.
neighbor
address
route-map
map-name
in
Configuration Examples for BGP Graceful Shutdown
This example gracefully shuts down the link to the specified neighbor in 600 seconds, adds the GSHUT community to the route, and sets a local preference of 500 for the route.
router bgp 1000 neighbor 2001:db8:5::1 remote-as 2000 neighbor 2001:db8:5::1 shutdown graceful 600 local-preference 500 neighbor 2001:db8:5::1 send-community exit
This example gracefully shuts down the link to the specified neighbor in 600 seconds, and adds the GSHUT community and numbered community to the route.
router bgp 1000 neighbor 2001:db8:5::1 remote-as 2000 neighbor 2001:db8:5::1 shutdown graceful 600 community 1400 neighbor 2001:db8:5::1 send-community exit
This example gracefully shuts down the link to the specified neighbor in 600 seconds, adds the GSHUT community and the numbered community to the route, and sets a local preference of 500 to the route.
router bgp 1000 neighbor 2001:db8:5::1 remote-as 2000 neighbor 2001:db8:5::1 shutdown graceful 600 community 1400 local-preference 500 neighbor 2001:db8:5::1 send-community exit
In additional to being able to gracefully shut down a BGP route, another use of the GSHUT community is to configure a community list to filter routes with this community from getting into the BGP routing table.
This example illustrates how to use a community list to filter incoming BGP routes based on the GSHUT community. In this example, a route map named RM_GSHUT denies routes based on a standard community list named GSHUT. The community list contains routes with the GSHUT community. The route map is then applied to incoming routes from the neighbor at 2001:db8:4::1.
router bgp 2000 neighbor 2001:db8:4::1 remote-as 1000 neighbor 2001:db8:4::1 activate neighbor 2001:db8:4::1 send-community exit route-map RM_GSHUT deny 10 match community GSHUT exit ip community-list standard GSHUT permit gshut router bgp 2000 neighbor 2001:db8:4::1 route-map RM_GSHUT in
Related Topic |
Document Title |
---|---|
Cisco IOS commands |
|
BGP commands |
Standard/RFC |
Title |
---|---|
RFC 6198 |
Requirements for the Graceful Shutdown of BGP Sessions |
Description |
Link |
---|---|
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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.
Feature Name |
Releases |
Feature Information |
---|---|---|
BGP Graceful Shutdown |
The BGP Graceful Shutdown feature reduces or eliminates the loss of traffic along a link being shut down for maintenance. Routers always have a valid route available during the convergence process. In Cisco IOS XE Release 3.7S, support was added for the Cisco ASR 903 router. The following commands were modified: ip community-list, neighbor shutdown, show ip bgp community, and show ip bgp vpnv4. |
|
BGP GSHUT Enhancement |
The BGP Graceful Shutdown (GSHUT) Enhancement feature enables graceful shutdown of either all neighbors or only virtual routing and forwarding (VRF) neighbors across BGP sessions. The following command was introduced: bgp graceful-shutdown all. |