System information
Troubleshooting X.25
Book Title
19-418
Possible Problem Solution
Incorrect cabling or bad router
hardware
Step 1 Use the show interfaces serial exec command to determine the
status of the interface.
Step 2 If the interface is down, refer to Chapter 15, “Troubleshooting Serial
Line Problems.” If the interface is up but the line protocol is down,
check the LAPB state in the output of the show interfaces serial
command.
Step 3 If the LAPB state is not CONNECT, use the debug lapb privileged
exec command (or attach a serial analyzer) to look for SABMs being
sent, and for UA packets being sent in reply to SABMs.
Step 4 If the show interfaces serial exec command indicates that the
interface and line protocol are up but no connections can be made,
there is probably a router or switch misconfiguration.
Step 5 Check all cabling and hardware for damage or wear. Replace cabling
or hardware as required. For more information, refer to Chapter 3,
“Troubleshooting Hardware and Booting Problems.”