I m having a problem with my cisco 1841.
From the router i can ping external ip(184.108.40.206 or 220.127.116.11). but a user from vlan 11 can ping router wan interface 18.104.22.168 and default gw 172.25.11.1, but can't ping external ip.
Can you remove ip nat inside from Physical interface & configure the same one under all subinteface.
Can you post output of sh ver (IOS Ver.)