Configuring Bgp Filtering By Neighbor - Cisco Catalyst 3550 series Software Configuration Manual

Configuring BGP
Command
Step 3 set ip next-hop ip-address [...ip-address]
[peer-address]
Step 4
end
Step 5
show route-map [map-name]
Step 6 copy running-config startup-config
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
section on page 31-86
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:
Command
Step 1
configure terminal
Step 2 router bgp autonomous-system
Step 3 neighbor {ip-address | peer-group name}
distribute-list {access-list-number | name}
{in | out}
Step 4 neighbor {ip-address | peer-group name}
route-map map-tag {in | out}
Step 5 end
Catalyst 3550 Multilayer Switch Software Configuration Guide
31-54
Purpose
(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.
Return to privileged EXEC mode.
Display all route maps configured or only the one specified to verify
configuration.
(Optional) Save your entries in the configuration file.
"Controlling Advertising and Processing in Routing Updates"
for information about the distribute-list command.
Purpose
Enter global configuration mode.
Enable a BGP routing process, assign it an AS number, and enter
router configuration mode.
(Optional) Filter BGP routing updates to or from neighbors as
specified in an access list.
You can also use the neighbor prefix-list router
Note
configuration command to filter updates, but you cannot use
both commands to configure the same BGP peer.
(Optional) Apply a route map to filter an incoming or outgoing
route.
Return to privileged EXEC mode.
Chapter 31 Configuring IP Unicast Routing
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