Cisco 3560G 48TS Software Configuration Guide - Page 661

Configuring BGP Filtering by Neighbor

Page 661 highlights

Chapter 30 Configuring IP Unicast Routing Configuring BGP Step 3 Command 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 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. 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" section on page 30-75 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 1 Step 2 Step 3 Step 4 Step 5 Command configure terminal router bgp autonomous-system neighbor {ip-address | peer-group name} distribute-list {access-list-number | name} {in | out} neighbor {ip-address | peer-group name} route-map map-tag {in | out} end 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. 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. (Optional) Apply a route map to filter an incoming or outgoing route. Return to privileged EXEC mode. 78-16156-01 Catalyst 3560 Switch Software Configuration Guide 30-53

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30-53
Catalyst 3560 Switch Software Configuration Guide
78-16156-01
Chapter 30
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”
section on page 30-75
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-lis
t 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.