Cisco Etherswitch adapter routing

I added a 16 port etherswitch adapter to a 2811 thinking I could use it as if I had a switch hanging off one of the f0/x ports without adding another box. I cant seem to get the switch ports to route to f0/0, f0/1, or s0/0/0. I defined a vlan but dont want to add another subnet if I dont have to. I would rather move the f0/0 subnet to the switch card and cable that way if it is required…. This cant be that complicated. what am I missing?