! R1 - core router
hostname R1
interface g0/0
 ip address 192.168.10.1 255.255.255.0
 no shutdown
interface g0/1
 ip address 10.10.12.1 255.255.255.252
 no shutdown
interface g0/2
 ip address 10.10.13.1 255.255.255.252
 no shutdown
ip route 192.168.20.0 255.255.255.0 10.10.12.2
ip route 192.168.20.0 255.255.255.0 10.10.13.2 200
router ospf 1
 router-id 1.1.1.1
 network 10.10.12.0 0.0.0.3 area 0
 network 10.10.13.0 0.0.0.3 area 0

! R2 - branch A
hostname R2
interface g0/0
 ip address 10.10.12.2 255.255.255.252
 no shutdown
interface g0/1
 ip address 10.10.23.1 255.255.255.252
 no shutdown
interface g0/2
 ip address 192.168.20.1 255.255.255.0
 no shutdown
router ospf 1
 router-id 2.2.2.2
 network 10.10.12.0 0.0.0.3 area 0
 network 10.10.23.0 0.0.0.3 area 0
 network 192.168.20.0 0.0.0.255 area 0

! R3 - branch B
hostname R3
interface g0/0
 ip address 10.10.13.2 255.255.255.252
 no shutdown
interface g0/1
 ip address 10.10.23.2 255.255.255.252
 no shutdown
interface g0/2
 ip address 192.168.30.1 255.255.255.0
 no shutdown
router ospf 1
 router-id 3.3.3.3
 network 10.10.13.0 0.0.0.3 area 0
 network 10.10.23.0 0.0.0.3 area 0
 network 192.168.30.0 0.0.0.255 area 0
