Problem with ISDN triggering

Unanswered Question
Feb 6th, 2008


while trying to fire ISDN from one of the access locations using DDR and using icmp , the call is established and i can see using debug ISDN commands like debug dialer events and debug isdn q931 , the o/p shows Multiple Frame Established at Layer 2 but 50% packets are dropped

response is something -- pattern like !.!.!.!.!

is this the problem with IOS or configuration issue

I have this problem too.
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Hi, i read you rpost and since ISDN setup depends on many devices for you the customer and the provider the telco, I wouldn't think right off hand that your problem is withthe IOS. ISDN layer 2 packets are use for signaling the protocol LAPD is used to ensure control and signaling information flows properly. You said you did a debug on layer 3 Q931 this is your user support layer, circuit and packet switched connections since you established a connection look like to problem is with layer 2. I would suggest troubleshooting the layer 2 BRI, have a read of the document below it should be helpful.

Richard Burts Wed, 02/06/2008 - 20:05


While Donald's post has some interesting comments and while troubleshooting layer 2 may be beneficial, I will suggest that if the debug q931 is showing call setup and establishment, then that is proof that layer 2 is functioning. You mention that you have done debug q931 but did not indicate what that debug shows. Perhaps you could include some of that?

I will also comment that when ping has a response pattern of !.!.! it is a classic symptom of a problem in which the routing table has 2 routes to the destination address but only one of the paths is actually passing traffic.

Perhaps if you would post some more of the details of the configuration, of what you are attempting to ping, and the output of show ip route we might get some insight into the problem.



syedsohailsarwar Fri, 02/08/2008 - 07:55

HI Rick

i ll be posting o/p of debug isdn q931 by tomorrow evening (IST time).

Well for pattern response of !.!.!.! i dont see that it is a problem with routing as we are using static routing in Branch/Access routers and to every destination we ahve two routes Leased Line as primary and ISDN as backup (AD of 20)

Richard Burts Fri, 02/08/2008 - 08:11


It would be helpful if you would do a screen capture of the ping attempt and of show ip route and post the output. The symptoms sound like there are 2 entries in the routing table of how to reach that destination (which might be your leased line and the ISDN).




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