int fa0/0
description R1 Fa0/0 to R2 Fa0/0
R1(config-if)#ip add 172.16.0.1 255.255.255.0
R1(config-if)#no shut
R1(config-if)#exit

R1#conf t
R1(config)#int fa0/1
R1(config-if)#description R1 Fa0/1 to R3 Fa0/0
R1(config-if)#ip add 10.0.1.1 255.255.255.0
R1(config-if)#no shut
R1(config-if)#exit

R1>
R1>ena
R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#router ospf 100
R1(config-router)#network 10.0.1.0 0.0.0.255 area 0
R1(config-router)#network 172.16.0.0 0.0.255.255 area 0
R1(config-router)#end
R1#
%SYS-5-CONFIG_I: Configured from console by console

R1#