Configuring BGP Route Reflectors | Explained with Examples

BGP requires that all iBGP speakers be fully meshed.
However, this requirement does not scale well when there are many iBGP speakers.
One way to reduce the iBGP mesh is to configure a route reflector.
The router with command "neighbor route-reflector-client" is the RR, and the neighbors at which the command points are the clients of that RR.
The combination of the RR and the clients is a "cluster". Other iBGP peers of the RR that are not clients are "nonclients".

Because there is a reflection of the iBGP learned routes, there can be a routing information loop.
The RR scheme has a few methods to avoid this loop:

1. originator-id — This is an optional, nontransitive BGP attribute that is 4 bytes long.
An RR creates this attribute. The attribute carries the router ID (RID) of the originator of the route in the local AS.
If, due to poor configuration, the routing information comes back to the originator, the information is ignored.
2. cluster-list — used by a RR to drop a route when it sees its own cluster ID in the route. This is used when you have multiple RRs fully-meshed to each other.


CONFIGURE
R1:
conf t
router bgp 1
neighbor 10.10.12.2 remote-as 1
network 1.1.1.1 mask 255.255.255.255
network 10.10.12.0 mask 255.255.255.0
end
wr

R2:
conf t
router bgp 1
neighbor 10.10.12.1 remote-as 1
neighbor 10.10.23.3 remote-as 1
network 10.10.12.0 mask 255.255.255.0
network 10.10.23.0 mask 255.255.255.0
end
wr
!
conf t
router bgp 1
neighbor 10.10.12.1 route-reflector-client
neighbor 10.10.23.3 route-reflector-client
end
wr

R3:
conf t
router bgp 1
neighbor 10.10.23.2 remote-as 1
network 10.10.23.0 mask 255.255.255.0
end
wr

VERIFY
show ip bgp 1.1.1.1
show ip bgp neighbors 10.10.23.3 advertised-routes


REFERENCES:
BGP Route Reflector
[ Ссылка ]

Route Reflectors
[ Ссылка ]

BGP Route Reflectors
[ Ссылка ]

BGP Route Reflection and Multiple Cluster IDs
[ Ссылка ]

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