294
Chapter 8
Configuring Basic BGP
the source router. An eBGP peer will have a different ASN than the source
router.
Now let's look at an example based on Figure 8.1. We'll add RouterB,
which is at 172.16.2.1, and identify the network in which to advertise to our
neighbor:
RouterB (config-router)#neighbor 172.16.2.1
remote-as 63001
The loopback IP address can be used for both iBGP and eBGP peers. Addi-
tional commands must be used when creating a peering session with a loop-
back interface. For iBGP sessions, the only additional command is the
update-source
command. The available syntaxes are as follows:
neighbor [
address | peer-group-name] update-source
interface-type interface-number
The IP address of the loopback should be used for the peer address. Since
the loopback interface is being used as the source of the BGP session, the
interface-type
should be entered as the loopback. The interface-
number
is the number of the loopback interface that is being used for BGP
peering. This is configured on the router using the loopback address.
The following command adds networks and creates a route in the BGP
table if the route is present in the IP table:
network
network-number
Let's look at an example adding our own network 63.78.0.0:
RouterA(config-router)#network 63.78.0.0 ?
backdoor Specify a BGP backdoor route
mask Network mask
route-map Route-map to modify the attributes
weight Set BGP weight for network
<cr>
RouterA(config-router)#network 63.78.0.0 mask
255.255.255.0 ?
backdoor Specify a BGP backdoor route
route-map Route-map to modify the attributes
weight Set BGP weight for network
<cr>
RouterA(config-router)#network 63.78.0.0 mask 255.255.0.0
RouterA(config-router)#
Copyright ©2001 SYBEX , Inc., Alameda, CA
www.sybex.com