Consider the topology below.
Imagine that R3 and R4 in Sparks, R5 and R6 are in Vegas and R1 in Reno and R2 in Wells. If Reno Route reflector goes down all remote locations will still able to get to all other locations.
Let's get started!!
First let's configure the interfaces, description, IGP (OSPF), BGP on all the remote routers R3, R4, R5, and R6.
|R3 and R4 Config|
|R5 and R6 Config|
|R1 and R2 Config|
|R1 and R2 BGP Config. Notice that all remote routes are route reflector client, however R1 and R2 are just iBGP peer.|
|All is well with BGP peers and routes are received as expected.|
|All the remote routers are also good to go. Note than R3 can ping the network on R6.|
|Show ip route to make sure the right routes are installed in the routing table.|
|Interface shutdown, lost connectivity to R1, BGP down with R1 and pinging R6's network still works through R2.|
As you can see if R1 goes down, all the routers will still have connectivity with everything.
Clear ip bgp
debug ip routing (as you may have recursive routing loops if IGP is not functioning properly)