Configuring Router on a stick

[kjjscharff]

For a classroom lab assignment, I am attempting to route several VLANS from a Catalyst 3524 switch via a Cisco 2621 router. The switch port on the switch is configured as a trunk switchport and is connected to F0/0 on the router. My problem is that when I attempt to use the command "encap ISL 10" command on the router F0/0.10 interface, the command is rejected. When I use the help menu, the "encap" command is not even listed. Is it possible my router IOS load does not support this feature? Does the switch need to be configured and connected to the router in order for ISL to be recognized? Any help would be appreciated.

The router IOS is: Version 12.1 (3r) T2, Release Software (fc1)

[r.crist]

You need to be running at least IP Plus code on the router to be able to configure sub-interfaces and trunk on the FE interface. Check the name of the binary file that the router is loading at boot. If it's not c2600-is-mz.121-3r.T2.bin, you'll need to download and tftp an IP Plus version of code.

[kjjscharff]

Thanks. I'll check out the boot file this evening.