Enterasys Networks Security Router X-PeditionTM - Manual (Page 162)

Overview
6-14 Configuring the Border Gateway Protocol
• Display all routes with any AS path:
– show ip bgp “.*”
• Display all routes having at least two AS numbers in the AS path:
– show ip bgp “. . + “
• Display all routes that traversed AS number 600:
– show ip bgp “.* 600 .*”
• Display all routes with beginning with AS number 300 and ending with AS number 800 in the
AS path:
– show ip bgp “^300 .* 800$”
Peer Groups
A BGP peer group is a set of BGP neighbors sharing update policies. Rather than define similar
policies for each individual neighbor, you can define a peer group and assign policies to the peer
group itself. If you modify options for the peer group, all members of the peer group inherit the
changes. You can also configure individual members to override those options that do not effect
outbound updates.
Peer-groups are comprised of either IBGP or EBGP members. IBGP group members must be in the
same AS as the peer-group, which itself must be in the same AS as the router. On the other hand,
when you create an EBGP peer-group, an AS number is not associated with the peer-group and all
peer-group members must belong to an AS other than the AS set for the router.
Do not mix IBGP and EBGP members in the same peer-group. Members of an EBGP group can be
from different ASs. A peer can belong to a single peer-group only.
A BGP peer group is configured by:
• Creating the peer group
• Assigning Options
• Adding neighbors
A BGP peer or peer group can be disabled without deleting all settings with the neighbor
shutdown command.
Creating a Peer Group
Create a BGP peer group and add a neighbor to it with the neighbor peer-group command.
Assigning Peer Group Options
A peer group is set with neighbor commands. Peer group members inherit all group options as
well as subsequent changes by default. They can also be configured to override those options not
pertinent to outbound updates.
Members of a peer group always inherit these attributes: remote-as (if configured), update-
source , neighbor filter-list , advertisement-interval , and next-hop-self .
You can set options for an particular neighbor by using any of the following commands with an IP
address. If you want to configure options for a peer group, configure any of the commands
employing the peer group name.
• Configure a BGP neighbor: neighbor remote-as number