BGP Route Reflector Configuration

Start from your working iBGP full mesh: three sessions on loopbacks, next-hop-self on edges, ping working.

Figure 1 – Starting point, the iBGP full mesh

Remove the R2–R4 Session

Tear down the direct session between edges on R2:

R2# configure terminal
R2(config)# router bgp 65002
R2(config-router)# no neighbor 4.4.4.4
%BGP-5-ADJCHANGE: neighbor 4.4.4.4 Down Neighbor deleted
R2(config-router)# end

Do the same on R4:

R4# configure terminal
R4(config)# router bgp 65002
R4(config-router)# no neighbor 2.2.2.2
R4(config-router)# end

Figure 2 – The R2–R4 session you just removed

What R2 Sees Now

Check the BGP table on R2:

R2# show ip bgp
BGP table version is 6, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
              t secondary path, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>   192.168.1.0      10.0.12.1                0             0 65001 i

The network 192.168.2.0/24 disappeared from R2.

R3 still holds the route, but split horizon prevents R3 from forwarding it to R2.

Figure 3 – R3 holds the route but cannot pass it on

Everything happens on R3.
Your clients keep their current configuration.

Figure 4 – Two sessions left, R3 is not a reflector yet

Declare the Clients

Configure R3 with one line per client:

R3# configure terminal
R3(config)# router bgp 65002
R3(config-router)# neighbor 2.2.2.2 route-reflector-client
%BGP-5-ADJCHANGE: neighbor 2.2.2.2 Down RR client config change
%BGP-5-ADJCHANGE: neighbor 2.2.2.2 Up
R3(config-router)# neighbor 4.4.4.4 route-reflector-client
%BGP-5-ADJCHANGE: neighbor 4.4.4.4 Down RR client config change
%BGP-5-ADJCHANGE: neighbor 4.4.4.4 Up
R3(config-router)# end

Each command resets the session.
Neighbors go down and come back up immediately.