User guide

BGP Overview Configuring BGP
page 4-10 OmniSwitch AOS Release 7 Advanced Routing Configuration Guide March 2015
Route Reflectors
Route reflectors are useful if the internal BGP mesh becomes very large. A route reflector is a
concentration router for other BGP peers in the local network, acting as a focal point for internal BGP
sessions.
Multiple client BGP routers peer with the central route server (the reflector). The router reflectors then
peer with each other. Although BGP rules state that routes learned through one IBGP speaker cannot be
advertised to another IBGP speaker, route reflection allows the router reflector servers to “reflect” routes,
thereby relaxing the IBGP standards.
The following illustration depicts two scenarios to demonstrate the benefit of using Route Reflectors:
In the diagram below, Clients 1, 2, and 3 peer with Reflector 1, and Clients 4, 5, and 6 peer with
Reflector2. Reflector 1 and 2 peer with each other. This allows each BGP speaker to maintain only one
BGP session, rather than a possible seven sessions, as in the diagram above.
:
AS 100 without Route Reflection
BGP Reflector 2
BGP Client 4
BGP Client 3
BGP Client 2
BGP Client 1
BGP Client 5
BGP Client 6
AS 100 with Route Reflection
BGP Reflector 1