Configuring The Bgp Route Reflector - 3Com 3C13636 Configuration Manual

3Com Router 3000 Ethernet Family
Configuration Guide

6.2.13 Configuring the BGP Route Reflector

To ensure the connectivity between IBGP peers, it is necessary to establish a fully
connected network. In some networks, there are large numbers of IBGP peers, and the
internal BGP networks become very large, consequently, the cost to establish a fully
meshed network is very high. Thus, it is required to utilize new peer technology. The
basic idea behind the route reflector conception is to specify a centralized router as the
focus of the internal sessions. Multiple BGP routers can peer one central point, and
then multiple route reflectors will peer again.
The route reflector is the centralized point of other routers, and other routers are called
the clients. A client and the route reflector are peers. They exchange routing
information with each other. The route reflector transfers (reflect) information among
clients in turn.
In the following figure, Router A receives an update message from an external peer and
transmits it to Router C. Router C is configured as the route reflector, with two clients,
Router A and Router B.
Router C reflects the update message from the client Router A to the client Router B.
Under this configuration, no peer session between Router A and Router B is virtually
needed because the router reflector will transmit the BGP information to Router B.
EBGP
Figure 6-1 Route reflector
A reflector is a router that performs the route reflection function. Its peers fall into two
categories: clients and non-clients. A route reflector and its clients constitute a cluster,
while all other peers in the AS, not belonging to the cluster, are non-clients. Use the
peer reflect-client command to specify the route reflector and add its clients.
The non-client peers and the route reflector must forms a fully connected network
because they have to follow the basic IBGP peer connectivity principle. A client can not
form peer relationship with any IBGP router outside its cluster. The route reflection
Router C
Route reflector
Update route
Router A
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Chapter 6 BGP Configuration
Reflected route
Router B
EBGP