Route Reflector is mechanism to avoid routing loops. Basically, when a route is learned via iBPG, it will not be advertised to another iBPG router within the same “Autonomous System.” It is the BPG split horizon rule. Therefore, routes learned via iBGP are never propagated to other iBGP peers.
There are three types of peering :
- eBPG neighbor
- iBGP client-neighbor
- iBGP non-client neighbor
An iBPG client neighbor will be “reflect” by the iBGP route reflector, whereas the iBGP non-client is just a regular iBGP neighbor.
Route reflector rules for forwarding routes:
- A route learned from an eBGP neighbor can be forwarded to another eBGP neighbor, client and non-client.
- A route learned from an client neighbor can be forwarded to another eBGP neighbor, client and non- client.
- A route learned from a non-client can be forwarded to another eBGP neighbor, but not to another non-client neighbor (Split Horizon loop prevention mechanism)
Commands to configure Route Reflector:
Router bgp <Autonomous System>
Neighbor x.x.x.x route-reflector-client
Note: This is just an example to configure the specific route reflector. An additional configuration might be required to make the route reflector work properly.