Fault Diagnosis and Troubleshooting of LAPB 241
[Router-x25-profile1]x25 vc-range in-channel 10 20 bi-channel 30
1024
[Router-x25-profile1]x25 pvc 1 interface serial 0 pvc 1
5Configure Serial 1.
aConfigure S1 as the Frame Relay interface.
[Router]interface serial 1
[Router-Serial1]link-protocol frame-relay
bConfigure a Frame Relay Annex G DLCI.
[Router-Serial1]fr dlci 100
[Router-fr-dlci-100]annexg dte
cApply the X.25 template to Annex G DLCI 100 (which is equivalent to
configure X.25 attributes for the Annex G DLCI).
[Router-fr-dlci-100]x25-template profile1
Fault Diagnosis and Troubleshooting of LAPB
Fault 1: Two connected sides use X.25 link layer protocol (or LAPB), but the
protocol is always disconnected. Turn on the debugging switch. It is found
that one end sends SABM frame, while the other end sends FRMR frame
circularly.
Troubleshooting: this is because both sides worked in the same working mode
(DTE or DCE). Change the working mode of one side to solve the problem.
Fault 2: Two connected sides use X.25 link layer protocol, and the protocol
is already in UP status, but cannot ping through the peer. Turn on the
debugging switch and it is found that the received frames are discarded
on one end instead of being forwarded up to the packet layer.
Troubleshooting: The maximum frame bits of this end may be too small. Change
the configuration.
Fault Diagnosis and Troubleshooting of X.25
This section describes some common faults and the troubleshooting methods.
Assuming that the connection of the X.25 layer 2 (LAPB) is completely correct.
Fault 1: LAPB is already in "Connect" status, but the X.25 protocol can not
enter "UP" status.
Troubleshooting: It is possible that the local working mode has been configured
wrong, for example, both sides of a connection are DTE or DCE. Try again after
changing the interface working mode.
Fault 2: X.25 protocol is "UP", but virtual circuit can not be established, i.e.,
unable to ping through.
This may be caused by one of the following:
■Local X.121 address not configured
■Address mapping to the peer not configured
■Opposite X.121 address not configured
■Address mapping from peer to local not configured
■Channel range not correct