Unanswered Question
Apr 3rd, 2009
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Dear Fiends,

Our branch router (1760) is having Problem with ISDN.if I given show ISDN status command,

ISDN BRI1/0 interface

dsl 0, interface ISDN Switchtype = basic-net3

Layer 1 Status:


Layer 2 Status:

TEI = 255, Ces = 1, SAPI = 0, State = ESTABLISH_AWAITING_TEI

Layer 3 Status:

0 Active Layer 3 Call(s)

CCB:callid=99F3, sapi=0, ces=1, B-chan=1, calltype=DATA, hdlctype=HDLC-T


CCB:callid=99F4, sapi=0, ces=1, B-chan=2, calltype=DATA, hdlctype=HDLC-T


Active dsl 0 CCBs = 2

The Free Channel Mask: 0x80000000

Number of L2 Discards = 3, L2 Session ID = 223

Total Allocated ISDN CCBs = 2

This message I am getting what could be the Problem.

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lamav Sat, 04/04/2009 - 06:18
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Its hard to say without seeing your configuration or knowing anything about the providers switch.

Are you sure you have configured the router to communicate with the correct type of telco switch?

Giuseppe Larosa Sun, 04/05/2009 - 05:09
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Hello Sasi,

your BRI interface is configured for ISDN switch type basic-net3 that is fine in Europe.

the sh isdn status indicates that the BRI is waiting to receive a TEI (a sort of MAC address to be used on the S-bus to address it) from the switch port.

This can come from different events like sh/no sh cycles on your BRI.

The switch can think that it has already provided a valid TEI and your BRI is stucked waiting for a valid TEI assignment.

Or simply the isdn switch is another type

The isdn layer1 is active.

Try the following:

save the configuration and reload the router if you can.

If this is not possible disable the BRI and wait few minutes before enabling it again

you can use

debug isdn q.921 to see the exchange of messages between the BRI and the switch port ( you need terminal monitor on the telnet/ssh session)

Also the isdn switch type needs to be checked with ISDN service provider.

Hope to help


smothuku Mon, 04/06/2009 - 03:06
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Hi ,

Check the voltage of ISDN ie ping no 4 and 5 of RJ jack which is terminating on NT box must be in between 96 to 102 Volts...

If you get the voltage then there no prob...try to reset NT box once..




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