Sure.. there are a few different ways to do this. You can use the serial ports and a pair of CSU/DSUs with a T1 back to back cable, T1-WICs with built in DSU/CSU and same cable, HSSI back to back if you have money to burn ;-). I have not tried the "normal" back to back cables at anything faster then 64K.. I'm told it fails but I suspect there are a few variables there.. quality of cable, length and so on. It might work with one of the 3 foot cables instead of the normal 10 footers.
Mike S
"Diplomacy; the art of saying 'nice doggie' till you can find a rock" Wynn Catlin