Session hangs
In diagnosing session hang or timeout problems, remember that TCPIPX25 does not track individual TCP sessions; it transfers only IP datagrams. One X.25 virtual circuit can carry datagrams from several TCP sessions. A VC can also be closed and reestablished several times during a TCP session with long periods of inactivity. Failure of an X.25 connection is not directly reflected in TCP sessions it might be carrying, only indirectly by TCP timeouts.
Opening a TCP session, such as a Telnet
connection, can fail for reasons not specific to X.25, such as a TCP/IP
routing problem caused by an incorrect 
BEGINROUTES
definition, or an IP routing problem in the remote device. Symptoms
suggesting these problems include:
BEGINROUTES definition, or an IP routing problem in the remote device. Symptoms
suggesting these problems include: - No X.25 call is made when a TCP connection is requested.
- No traffic is received from the remote equipment, indicated by a received count of zero in the EZB2351I connection terminated message.
An established TCP connection can hang because the X.25 network or remote device is down. This is indicated by a clear cause and diagnostic, as described in Steps for diagnosing logon problems.