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New Member

DDR&ISDN problem working


after upgrade from 12.0.7T to 12.1.16 on 3640, i have problem on dialer backup. If i shutdown the bri with the dialer active, or in call state, there is no mode to create a feature backup connection. I have tried to recreate another dialer, destroy the pool association with the bri without any good result. Only reloading the router can permit to have a new "debug isdn q931" output.

Please note the ISDN is a point-to-point BRI NT1 and the interface has the static-tei 0.



Cisco Employee

Re: DDR&ISDN problem working

Not exactly sure what you are trying to do..But i think you are trying to configure a backup for ISDN bri line..using dialer interfaces..right?

You can't configure a backup for a DDR capable line like ISDN using "backup interface xxx" command. You need to use a floating statis routes or dialer watch function for that. Here is the link which explains all three methods for backup.

It also has sample config links too.

Again, explain more about the actual problem and what you are trying to do if i have mis-understood your question.

New Member

Re: DDR&ISDN problem working


excuse me for my poor explanation. The problem is: after upgrade to 12.1.16 from 12.0.7T, my backup doesn't work (i'm using floating static).

The problem is:

1) the primary link goes down (for ex. disconnect v35 cable)

2) the floating static trigger the dialer (i see in "debug isdn q931).

3) the backup connection is up.

4) NOW i shut down the dialer (i see a message there is a call) on console

5) Immediatly, i shut down the bri too.

6) NO Connection to remote site

7) I restart dialer & bri (no shut command)

8) PROBLEM: No any call to remote site. The only solution is reload the router.

All these operation i have made, worked correctly on previuos ios where i hadn't the necessity to restart the 3640.



New Member

Re: DDR&ISDN problem working

G. Pozzo

I have a few questions:

Can you post the config for this router?

When the backup link came up initially, were you able to transmit and receive traffic across the backup link?

What was the output of SHOW ISDN STATUS just prior to the reload?

Was there any dialer activity in debug after the NO SHUTDOWN command?

How long did you wait before the reload?

New Member

Re: DDR&ISDN problem working

Hi, i respond you to points:

1) I have difficult to post the router config

2) Yes, the backup, previous this works correctly

3) The status of ISDN is: L1 Active, L2 Multiframe est.., L3 active & working

4) No after "no shut" no any debug activity regards dialer

5) From few seconds, to 3 minutes.


Cisco Employee

Re: DDR&ISDN problem working

Thanks for explanation.

For DDR link there has to be the interresting traffic flowing to trigger the call. So when you issue "shut/no shut" for bri and dialer interface, you need to generate the interesting traffic like ping etc..

Now after you issue "shut/no shut" on bri interface issue

sh isdn status

and verify that layer 2 status is "Multiple frame established"

If it is, enable following debug after you issue "shut/no shut"

debug dialer

debug isdn q931

debug ppp nego

After that generate a ping for interesting traffic and see what is the debug you see.

New Member

Re: DDR&ISDN problem working

First, Thanks for your interesting.

Yes, i have interesting traffic, like ping, telnet and soon.

After shut/noshut, the ISDN L2 is correctly setted to "MULTIFRAME_ESTABLISHED", and with "debug isdn q921" i can see my bri interface talking with NT1, and viceversa.

NO any other "debug dialer", "debug isdn q931", "debug ppp negotiation" after the last noshut command. I have tried for two hours without result and the access-list of dialer-list mark interesting packet but the dialer was always down.

Cisco Employee

Re: DDR&ISDN problem working

Its little diffucult to troubleshoot this issue here now..So pl. open a tac case for this issue by logging at

New Member

Re: DDR&ISDN problem working

Thanks for all the time spent.

I'll try the last solution before open the tac. Tomorrow night, i'll test the same scenario with 12.1.18 ios version.

If it will not work i'll open a tac.

Best Regards


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