Dell FCX624-S Laptop User Manual


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PowerConnect B-Series FCX Configuration Guide 987
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BGP4 graceful restart
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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,
switchover, failover, or hitless OS upgrade. 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.
NOTE
BGP4 graceful restart is supported in PowerConnect B-Series FCX switches in a stack . If the switch
will 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 BGP4
For details concerning configuration of BGP4 graceful restart, refer to “Configuring BGP4 graceful
restart” on page 1025.
Basic configuration and activation for BGP4
BGP4 is disabled by default. Follow the steps below to enable BGP4 and place your 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.