اینم یک نمونه کانفیگ که بدون هیچ اشکالی داره کار میکنه
ip name-server 4.2.2.1
ip name-server 192.9.9.3
!
!
interface FastEthernet0
ip address 192.168.0.1 255.255.255.0
ip nat inside
duplex auto
speed auto
no cdp enable
!
interface Serial0
ip address 217.219.x.x 255.255.255.240
ip nat outside
encapsulation ppp
no cdp enable
!
ip classless
ip route 0.0.0.0 0.0.0.0 Serial0
!
no ip http server
ip nat inside source list 10 interface Serial0 overload
!
access-list 10 permit 192.168.0.0 0.0.0.255
no cdp run
!
control-plane
!
line con 0
line aux 0
line vty 0 4
!
end