3com 3031 Instruccion De Instalación

C

HAPTER

 26: X.25 

AND

 LAPB C

ONFIGURATIONS

Problem solving: Perform the following procedure to remove the fault.

■

Enable the debug switch and discover one end sending SABM frame, while the 
other sending FRMR frame cyclically.

■

The symptom indicates that two sides are working in the same mode (DTE or 
DCE). Change the working mode of one side to solve it. 

Fault 2: the link layer protocol of two connected sides is X.25, which has been in 
UP status, but unable to 

 through.

Problem solving: Perform the following procedure remove the fault.

■

 Enable the debug switch and discover that one end discards the received 
frame and does not transmit it to the packet layer.

■

The maximum frame bit number of this end may be too small. Change the 
configuration.

This section describes some common faults and their solutions. Though the cases 
here cannot cover all faults, they are helpful in the troubleshooting of common 
faults.

Assume that the layer 2 connection (LAPB) of X.25 is completely correct.

Fault 1: LAPB is already in "Connect" status, but the X.25 protocol can not enter 
"UP" status.

Problem solving: Perform the following procedure remove the fault.

■

It is possible that the local operating mode is not correctly configured, for 
example, both sides of a connection are DTE or DCE. Retry after changing the 
working mode of the interface.

Fault 2: X.25 protocol is "UP", but virtual circuit can not be established, i.e., 
unable to 

 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.

■

Inhibitive facility options carried.

Problem solving: Perform the following procedure remove the fault.

■

If the addresses are configured improperly, modify them to the correct 
configurations.

■

For the two last causes, consult the network administration.

Fault 3: The virtual circuit can be set up, but is frequently reset or cleared during 
data transmission.