38-64
Cisco Catalyst Blade Switch 3130 and 3032 for Dell Software Configuration Guide
OL-12247-04
Chapter 38 Configuring IP Unicast Routing
Configuring BGP
To configure a BGP confederation, you must specify a confederation identifier that acts as the
autonomous-system number for the autonomous-system group.
Beginning in privileged EXEC mode, use these commands to configure a BGP confederation:
Configuring BGP Route Reflectors
BGP requires that all of the IBGP speakers be fully meshed. When a router receives a route from an
external neighbor, it must advertise it to all internal neighbors. To prevent a routing information loop,
all IBPG speakers must be connected. The internal neighbors do not send routes learned from internal
neighbors to other internal neighbors.
With route reflectors, all IBGP speakers do not need to be fully meshed. When you configure an internal
BGP peer as a
route reflector
, it passes IBGP learned routes to a set of IBGP neighbors. The internal
peers of the route reflector are divided into
client peers
and
nonclient peers (
all the other routers in the
autonomous system). A route reflector reflects routes between these two groups. The route reflector and
its client peers form a
cluster
. The nonclient peers must be fully meshed with each other, but the client
peers need not be fully meshed. The clients in the cluster do not communicate with IBGP speakers
outside their cluster.
When the route reflector receives an advertised route, it takes one of these actions, depending on the
neighbor:
•
A route from an external BGP speaker is advertised to all clients and nonclient peers.
•
A route from a nonclient peer is advertised to all clients.
•
A route from a client is advertised to all clients and nonclient peers. Hence, the clients need not be
fully meshed.
Usually, a cluster of clients have a single route reflector, and the cluster is identified by the route reflector
router ID. To increase redundancy and to avoid a single point of failure, a cluster can have more than one
route reflector. In this case, you must configure all route reflectors in the cluster with the same 4-byte
cluster ID so that a route reflector recognizes updates from route reflectors in the same cluster. All the
route reflectors serving a cluster should be fully meshed and should have identical sets of client and
nonclient peers.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
router bgp
autonomous-system
Enter BGP router configuration mode.
Step 3
bgp confederation identifier
autonomous-system
Configure a BGP confederation identifier.
Step 4
bgp confederation peers
autonomous-system
[
autonomous-system autonomous-system
...]
Specify the autonomous systems that belong to the
confederation and that are treated as special EBGP peers.
Step 5
end
Return to privileged EXEC mode.
Step 6
show ip bgp neighbor
show ip bgp network
Verify the configuration.
Step 7
copy running-config startup-config
(Optional) Save your entries in the configuration file.
