Dell BigIron RX Series, Configuration Manual

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BigIron RX Series Configuration Guide 851
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Displaying BGP4 information
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match address-filters 11
set community 11:12 no-export
route-map permit1122 permit 12
match ip address 11
route-map permit1122 permit 13
match ip address std_22
This example shows that the running configuration contains six route maps. Notice that the match
and set statements within each route map are listed beneath the command for the route map
itself. In this simplified example, each route map contains only one match or set statement.
To display the active configuration for a specific route map, enter a command such as the following,
which specifies a route map name.
BigIron RX# show route-map setcomm
route-map setcomm permit 1
set community 1234:2345 no-export
This example shows the active configuration for a route map called “setcomm“.
Syntax: show route-map [ <map-name> ]
Graceful restart in BGP
Under normal operation, restarting a BGP router causes the network to be reconfigured. In this
situation, routes available through the restarting router are first deleted when the router goes down
and are then rediscovered and re-added to the routing tables when the router is back up and
running. In a network where routers are restarted regularly, this can degrade performance
significantly and limit the availability of network resources. BGP graceful restart dampens the
network topology changes and limits route flapping by allowing routes to remain available between
routers during a restart. BGP Graceful restart operates between a router and its peers and must be
configured on both the router and its peers.
A BGP router with graceful restart enabled advertises its graceful restart capability and restart
timer to establish peering relationships with other routers. Once the restarting router is restarted, it
begins to reestablish BGP connections and receive routing updates from its peers. When the
restarting router receives all end-of-RIB markers from its helper neighbors, all of the routes are
recomputed, and newly computed routes replace the stale routes in the routing table. An
end-of-RIB marker indicates that it has received all of the BGP route updates.
During the restarting process, the helper neighbors will continue to use all of the routes learned
from the restarting router and mark them as stale for the length of the learned restart timer. If the
restarting router doesn't come back up within the restart timer, the routes marked stale will be
removed.
Configuring BGP graceful restart
To configure BGP Graceful Restart, you must enable it on all BGP peers where you want it to
operate and set the following timers:
•
Restart Timer
•
Stale Routes Timer