PowerConnect B-Series FCX Configuration Guide 98753-1002266-01BGP4 graceful restart 30BGP4 graceful restartBGP4 graceful restart is a high-availability routing feature that minimizes disruption in trafficforwarding, diminishes route flapping, and provides continuous service during a system restart,switchover, failover, or hitless OS upgrade. During such events, routes remain available betweendevices. BGP4 graceful restart operates between a device and its peers, and must be configuredon each participating device.Under normal operation, when a BGP4 device is restarted, the network is automaticallyreconfigured. Routes available through the restarting device are deleted when the device goesdown, and are then rediscovered and added back to the routing tables when the device is back upand running. In a network with devices that are regularly restarted, performance can degradesignificantly and the availability of network resources can be limited.BGP4 graceful restart is enabled globally by default. A BGP4 graceful restart-enabled deviceadvertises this capability to establish peering relationships with other devices. When a restartbegins, neighbor devices mark all of the routes from the restarting device as stale, but continue touse the routes for the length of time specified by the restart timer. After the device is restarted, itbegins to receive routing updates from the peers. When it receives the end-of-RIB marker thatindicates it has received all of the BGP4 route updates, it recomputes the new routes and replacesthe stale routes in the route map with the newly computed routes. If the device does not come backup within the time configured for the purge timer, the stale routes are removed.NOTEBGP4 graceful restart is supported in PowerConnect B-Series FCX switches in a stack . If the switchwill function as a restart helper device only, a secondary management module is not required.This implementation of BGP4 graceful restart supports the Internet Draft-ietf-idr-restart-10.txt:restart mechanism for BGP4For details concerning configuration of BGP4 graceful restart, refer to “Configuring BGP4 gracefulrestart” on page 1025.Basic configuration and activation for BGP4BGP4 is disabled by default. Follow the steps below to enable BGP4 and place your Layer 3 Switchinto service as a BGP4 router.1. Enable the BGP4 protocol.2. Set the local AS number.NOTEYou 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.
