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Unanswered Question
Jun 4th, 2001
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I have a problem with VoIP over ISDN BRI connection in the following configuration:


Connection between routers and PBXs is made by ISDN BRI using VIC-2BRI-NT/TE in routers.

Ports BRI on routers are configured as NT (network side).

Routers are connected together with leased line (2Mb/s).

When phoneA initiates voice call to phoneB following is happened :

1. routerA transmits VoIP packets to routerB,

2. routerB transmits one SETUP frame (ITU Q.931) to PBXb; after 4 seconds next SETUP


3. PBXb is not responding

4. after few seconds routerA transmits DISCONNECT to PBXa with cause=0x80A2 No circuit/channel available

Transmitted numbers are correct. Layer1 and 2 - correct.

If anybody is interested - I have logs from debug isdn q931 and debug voice ccapi inout.

Thank you for any suggestions.


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dgoodwin Mon, 06/04/2001 - 07:15
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  • Cisco Employee,

The log of debug isdn q931 on routerB would be helpful here. But I am thinking that we need to figure out why when we send a Q.931 SETUP message to the PBXb that it does not respond. Most likely the problem is there.

sarvesh.mishra Wed, 06/06/2001 - 04:34
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We would like to know we can enable load balancing & Dial backup between two unequal cost links in 1750 router or not. We are using ISDN BRI and Leased line and a choice of OSPF,IGRP & EIGRP.

lferre Thu, 07/12/2001 - 04:14
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could you post the configuration of your router?


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