interface Loopback0
ip address 192.168.20.1 255.255.255.0
# Configuring RIP route protocol
router rip
version 2
network 192.168.12.0
network 192.168.20.0
Configuration of Device C:
# Configuring Ethernet interface
interface FastEthernet0/0
ip address 192.168.12.3 255.255.255.0
#Configure the loopback port
interface Loopback0
ip address 192.168.30.1 255.255.255.0
# Configuring RIP route protocol
router rip
version 2
network 192.168.12.0
network 192.168.30.0