Today I was dinking around on the switch portion of a 6500 switch, and decided I wanted to jump into the router part (technically speaking, the MSFC — the multi-layer switch feature card). [Note: this is only going to make sense if you're running a hybrid 6500 (catOS + IOS on the RP).] This is easily done by using the session 15 (or session 16, if you’re trying to go to your redundant supervisor) command.
Switch> (enable) sess?
session Tunnel to ATM or Router module
My attempt, however, was swatted down. In consolation, I was given a cryptic error message:
Switch> (enable) session 15
Trying Router-15...
session: Unable to tunnel to Router-15 (57)