Allied Telesis AR300 series manual How to troubleshoot Isdn, Info

How to troubleshoot ISDN

Step 1: Is the router communicating with the ISDN network at the signalling level?

When the router is connected to the ISDN network, either by plugging it into an NT1 if the router has an S/T interface, or by plugging it directly into the ISDN network if the router has a U interface, it establishes a low-level connection to the network. Basically, the router and the network device exchange a particular set of waveforms. When the router is satisfied that it has seen the correct waveforms, it considers the low-level connection to be established, and the link is now ready to send data frames.

There are two ways to determine whether or not the router considers that the connection is established:

1.Look at the external LED marked "Active". This will be lit when the connection is established.

2.At the command prompt, enter the command:

show bri=n state

where n is the number of the BRI interface under consideration. Interfaces are numbered from 0.

An example of the output of the show bri=0 state command is shown in the following figure.

State for BRI instance 0:

Interface type	TE
State	Activated
Rx INFO	INFO 4
Tx INFO	INFO 3
Activate request ...	no
Activated	yes
Synchronised	yes
Activation mode ....	normal
Mode	ISDN
ISDN slots	B1, B2
D channel class ....	high
B1 enabled	no
B2 enabled	no
B1, B2 aggregated...	no
Rx multiframing ....	no
Transceiver mask ..	56

The important item in this output is the second item, State. This must be shown as Activated. If it has any other value (Inactive, Awaiting Signal, Synchronized, etc.) then the connection has not yet been established.

If the BRI interface is Activated, then the problem lies at a higher level. Go to "Step 2: Is the router communicating with the ISDN network at the LAPD level?" on page 4.

2