http://www.cisco.com/univercd/cc/td/doc/cisintwk/idg4/nd2002.htm#xtocid22927... grep GRE "Cisco's Generic Routing Encapsulation (GRE) multiprotocol carrier protocol encapsulates IP, CLNP, IPX, AppleTalk, DECnet Phase IV, XNS, VINES, and Apollo packets inside IP tunnels."... assuming you're running Cisco gear, anyhow. -carl hirsch network analyst sargent & lundy llc