BGP and BGP4+ Introduction

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:

awplus(router-config)#

neighbor <neighborid> This command configures the local router as a BGP route route-reflector-clientreflector and the specified neighbor as a client.

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:

awplus(router-config)#

bgp cluster-id{<ip-address>This command configures the cluster-id if the BGP cluster has <cluster-id>}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. .

Use the show ip bgp (BGP) command in Privileged Exec mode to display the originator ID and the cluster-list attributes.

 

Software Reference Supplement for SwitchBlade® x8112, x908, x900 and x610 Series Switches

 

C613-50032-01 REV D

AlliedWare PlusTM Operating System - Software Version 5.4.3-2.6

1.33

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Allied Telesis VERSION 5.4.3-2.6, BGP4 manual BGP Route Reflectors