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BGP and BGP4+ Introduction
Software Reference Supplement for SwitchBlade® x8112, x908, x900 and x610 Series Switches
C613-50032-01 REV D AlliedWare Plus
TM
Operating System - Software Version 5.4.3-2.6 1.33
BGP Route Reflectors
BGP requires that all iBGP speakers be fully meshed. Another way to reduce the iBGP mesh
is to configure a BGP route reflector, instead of configuring a BGP confederation.
With route reflectors, all iBGP speakers need not be fully meshed because there is a
method to pass learned routes to neighbors. In this model, an iBGP peer is configured to
be a route reflector responsible for passing iBGP learned routes to a set of iBGP neighbors.
The internal peers of the route reflector are divided into two groups: client peers and all
the other routers in the autonomous system (non-client peers). A route reflector reflects
routes between these two groups.
The route reflector and its client peers form a cluster. The non-client 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, depending on the neighbor, it takes
the following actions:
■ A route from an external BGP speaker is advertised to all clients and non-client peers.
■ A route from a non-client peer is advertised to all clients.
■ A route from a client is advertised to all clients and non-client peers. Hence, the clients
need not be fully meshed.
To configure a route reflector and its clients, use the command below in Router
Configuration mode:
Along with route reflector-aware BGP speakers, you can have BGP speakers that do not
understand the concept of route reflectors. They can be members of client or non-client
groups allowing a gradual migration from the old BGP model to the route reflector model.
An autonomous system can have multiple route reflectors. A route reflector treats other
route reflectors just like other iBGP speakers. A route reflector can be configured to have
other route reflectors in a client group or non-client group.
Each route reflector would be configured with other route reflectors as non-client peers,
so the route reflectors will be fully meshed. The clients are configured to maintain iBGP
sessions with only the route reflector in their cluster.
If the cluster has more than one route reflector, configure the cluster ID by using the
following command in Router Configuration mode:
Use the show ip bgp (BGP) command in Privileged Exec mode to display the originator ID
and the cluster-list attributes.
awplus(router-config)#
neighbor <neighborid>
route-reflector-client
This command configures the local router as a BGP route
reflector and the specified neighbor as a client.
awplus(router-config)#
bgp cluster-id {<ip-address>|
<cluster-id>}
This command configures the cluster-id if the BGP cluster has
more than one route reflector. A cluster includes one or more
route reflectors and their clients. Usually, each cluster is
identified by the router-id of its single route reflector. .