31-49
Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 31 Configuring IP Unicast Routing
Configuring BGP
Use the no router bgp autonomous-system global configuration command to remove a BGP AS. Use the
no network network-number router configuration command to remove the network from the BGP table.
Use the no neighbor {ip-address | peer-group-name} remote-as number router configuration command
to remove a neighbor. Use the no neighbor {ip-address | peer-group-name} remove-private-as router
configuration command to include private AS numbers in updates to a neighbor. Use the
synchronization router configuration command to re-enable synchronization.
These examples show how to configure BGP on the routers in Figure 31-5.
Router A:
Switch(config)# router bgp 100
Switch(config-router)# neighbor 129.213.1.1 remote-as 200
Router B:
Switch(config)# router bgp 200
Switch(config-router)# neighbor 129.213.1.2 remote-as 100
Switch(config-router)# neighbor 175.220.1.2 remote-as 200
Router C:
Switch(config)# router bgp 200
Switch(config-router)# neighbor 175.220.212.1 remote-as 200
Switch(config-router)# neighbor 192.208.10.1 remote-as 300
Router D:
Switch(config)# router bgp 300
Switch(config-router)# neighbor 192.208.10.2 remote-as 200
To verify that BGP peers are running, use the show ip bgp neighbors privileged EXEC command. This
is the output of this command on Router A:
Switch# show ip bgp neighbors
BGP neighbor is 129.213.1.1, remote AS 200, external link
BGP version 4, remote router ID 175.220.212.1
BGP state = established, table version = 3, up for 0:10:59
Last read 0:00:29, hold time is 180, keepalive interval is 60 seconds
Minimum time between advertisement runs is 30 seconds
Received 2828 messages, 0 notifications, 0 in queue
Sent 2826 messages, 0 notifications, 0 in queue
Connections established 11; dropped 10
Anything other than state = established means that the peers are not running. The remote router ID is
the highest IP address on that router (or the highest loopback interface). Each time the table is updated
with new information, the table version number increments. A table version number that continually
increments means that a route is flapping, causing continual routing updates.
Step 9
bgp fast-external-fallover (Optional) Automatically reset a BGP session when a link
between external neighbors goes down. By default, the session
is not immediately reset.
Step 10
end Return to privileged EXEC mode.
Step 11
show ip bgp network network-number
show ip bgp neighbor
Verify the configuration.
Step 12
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
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