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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 31 Configuring IP Unicast Routing
Configuring BGP
Use the no route-map map-tag command to delete the route map. Use the no set ip next-hop ip-address
command to re-enable next-hop processing.
Configuring BGP Filtering by Neighbor
You can filter BGP advertisements by using AS-path filters, such as the as-path access-list global
configuration command and the neighbor filter-list router configuration command. You can also use
access lists with the neighbor distribute-list router configuration command. Distribute-list filters are
applied to network numbers. See the
“Controlling Advertising and Processing in Routing Updates”
for information about the distribute-list command.
You can use route maps on a per-neighbor basis to filter updates and to modify various attributes. A route
map can be applied to either inbound or outbound updates. Only the routes that pass the route map are
sent or accepted in updates. On both inbound and outbound updates, matching is supported based on AS
path, community, and network numbers. Autonomous system path matching requires the match as-path
access-list route-map command, community based matching requires the match community-list
route-map command, and network-based matching requires the ip access-list global configuration
command.
Beginning in privileged EXEC mode, follow these steps to apply a per-neighbor route map:
Step 3
set ip next-hop ip-address [...ip-address]
[peer-address]
(Optional) Set a route map to disable next-hop processing
•
In an inbound route map, set the next hop of matching routes to
be the neighbor peering address, overriding third-party next hops.
•
In an outbound route map of a BGP peer, set the next hop to the
peering address of the local router, disabling the next-hop
calculation.
Step 4
end
Return to privileged EXEC mode.
Step 5
show route-map [map-name]
Display all route maps configured or only the one specified to verify
configuration.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Command
Purpose
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
router bgp autonomous-system
Enable a BGP routing process, assign it an AS number, and enter
router configuration mode.
Step 3
neighbor {ip-address | peer-group name}
distribute-list {access-list-number | name}
{in | out}
(Optional) Filter BGP routing updates to or from neighbors as
specified in an access list.
Note
You can also use the neighbor prefix-list router
configuration command to filter updates, but you cannot use
both commands to configure the same BGP peer.
Step 4
neighbor {ip-address | peer-group name}
route-map map-tag {in | out}
(Optional) Apply a route map to filter an incoming or outgoing
route.
Step 5
end
Return to privileged EXEC mode.