R1:
R1#configure terminal
R1(config)#interface f0/1
R1(config-if)#ip address 192.168.12.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#router eigrp 100
R1(config-router)#network 192.168.12.0 0.0.0.255
R1(config)#interface f0/1
R1(config-if)#ip address 192.168.12.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#router eigrp 100
R1(config-router)#network 192.168.12.0 0.0.0.255
R2:
R2#configure terminal
R2(config)#interface f0/0
R2(config-if)#ip address 192.168.12.2 255.255.255.0
R2(config-if)#no shutdown
R2(config)#interface f0/1
R2(config-if)#ip address 192.168.23.2 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#router eigrp 100
R2(config-router)#network 192.168.12.0 0.0.0.255
R2(config-router)#network 192.168.23.0 0.0.0.255
R2(config)#interface f0/0
R2(config-if)#ip address 192.168.12.2 255.255.255.0
R2(config-if)#no shutdown
R2(config)#interface f0/1
R2(config-if)#ip address 192.168.23.2 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#router eigrp 100
R2(config-router)#network 192.168.12.0 0.0.0.255
R2(config-router)#network 192.168.23.0 0.0.0.255
R3:
R3#configure terminal
R3(config)#interface f0/0
R3(config-if)#ip address 192.168.23.3 255.255.255.0
R3(config-if)#no shutdown
R3(config-if)#exit
R3(config)#router eigrp 100
R3(config-router)#network 192.168.23.0 0.0.0.255
R3(config)#interface f0/0
R3(config-if)#ip address 192.168.23.3 255.255.255.0
R3(config-if)#no shutdown
R3(config-if)#exit
R3(config)#router eigrp 100
R3(config-router)#network 192.168.23.0 0.0.0.255