i have 1 internet router C-2600 as a gateway to internet via fastethernet. The router has 3 ports, 1 is integrated (fe0/0) and another 2 is physical card-port(sub-interface fe0/0.1 and fe0/0.2).This is supposed to be simple routing to internet via fe (external) and fe (internal local LAN). The problem is i cannot assign any IP address to sub-interface port (fe0/0.1 or fe0/0.2) as the router complains something about " cannot assign Ip address unless interface is in IEEE802.1, Trunking or IS-VLAN". I need to use 1 sub-interface port external to Internet (gateway) and another 1 port internal to local LAN (via firewall). i check the IOS and it doesn't have any option for encapsulation command.
thanks in advance