X.25 troubleshooting is a complicated subject that deserves in-depth discussion. The WAN GUI is intuitive to use. Briefly, if the WAN Service doesn't start, first review the Node and modem type, then the Packet format, then the X.25 Version and Data Link Layer parameters. For X.25 line troubleshooting, you can use the X.25 card manufacturer's troubleshooting utility (e.g., Ecmodule for the Eicon cards).