Bgp4 graceful restart, Basic configuration and activation for bgp4 – Brocade Communications Systems Layer 3 Routing Configuration ICX 6650 User Manual
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Brocade ICX 6650 Layer 3 Routing Configuration Guide
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BGP4 graceful restart
BGP4 graceful restart
BGP4 graceful restart is a high-availability routing feature that minimizes disruption in traffic
forwarding, diminishes route flapping, and provides continuous service during a system restart.
During such events, routes remain available between devices. BGP4 graceful restart operates
between a device and its peers, and must be configured on each participating device.
Under normal operation, when a BGP4 device is restarted, the network is automatically
reconfigured. Routes available through the restarting device are deleted when the device goes
down, and are then rediscovered and added back to the routing tables when the device is back up
and running. In a network with devices that are regularly restarted, performance can degrade
significantly and the availability of network resources can be limited.
BGP4 graceful restart is enabled globally by default. A BGP4 graceful restart-enabled device
advertises this capability to establish peering relationships with other devices. When a restart
begins, neighbor devices mark all of the routes from the restarting device as stale, but continue to
use the routes for the length of time specified by the restart timer. After the device is restarted, it
begins to receive routing updates from the peers. When it receives the end-of-RIB marker that
indicates it has received all of the BGP4 route updates, it recomputes the new routes and replaces
the stale routes in the route map with the newly computed routes. If the device does not come back
up within the time configured for the purge timer, the stale routes are removed.
This implementation of BGP4 graceful restart supports the Internet Draft-ietf-idr-restart-10.txt:
restart mechanism for BGP4
For details concerning configuration of BGP4 graceful restart, refer to
Basic configuration and activation for BGP4
BGP4 is disabled by default. Follow the steps below to enable BGP4 and place your Brocade Layer
3 switch into service as a BGP4 router.
1. Enable the BGP4 protocol.
2. Set the local AS number.
NOTE
You must specify the local AS number for BGP4 to become functional.
3. Add each BGP4 neighbor (peer BGP4 router) and identify the AS the neighbor is in.
4. Save the BGP4 configuration information to the system configuration file.
NOTE
By default, the Brocade router ID is the IP address configured on the lowest numbered loopback
interface. If the Layer 3 switch does not have a loopback interface, the default router ID is the lowest
numbered IP interface address configured on the device. For more information or to change the
router ID, refer to
on page 31. If you change the router ID, all current BGP4
sessions are cleared.