The configuration of Router A:
!
router bgp 100
bgp log-neighbor-changes
neighbor ibgp-group peer-group
neighbor ibgp-group description peer in the same as
neighbor 192.168.6.2 remote-as 100
neighbor 192.168.6.2 peer-group ibgp-group
neighbor 192.168.6.2 description one peer in the ibgp-group
neighbor 192.168.7.9 remote-as 100
neighbor 192.168.7.9 peer-group ibgp-group
The configuration of Router B:
!
router bgp 100
bgp log-neighbor-changes
neighbor ibgp-peer peer-group
neighbor ibgp-peer remote-as 100
neighbor ibgp-peer route-map ibgp-rmap out
neighbor 192.168.5.3 peer-group ibgp-peer
neighbor 192.168.5.3 route-map set-localpref in
neighbor 192.168.6.3 peer-group ibgp-peer
The configuration of Router C:
!
router bgp 100
bgp log-neighbor-changes
neighbor ibgp-group peer-group
neighbor 192.168.5.2 remote-as 100
neighbor 192.168.5.2 peer-group ibgp-group
neighbor 192.168.7.7 remote-as 100
neighbor 192.168.7.7 peer-group ibgp-group