interface fa0/0
description****inside interface*****
ip address x.x.x.x x.x.x.x
ip nat inside
interface serial 0/0
description*****outside interface****
ip address x.x.x.x x.x.x.x
ip nat outside
ip nat pool overld 10.155.132.100 10.155.132.100 netmask x.x.x.x
ip nat inside source list 1 pool overld overload
access-list 1 permit 172.16.0.0 0.0.255.255
HTH..rate if helpful..