ISDN issue

Unanswered Question
Jul 28th, 2009

I have one cisco 1841 router in which is isdn is not working. Layer 1 Status:DEACTIVATED and getting **ERROR**: host_disconnect_ack: Call rejected cause No circuit/channel available(0x22) call id 0x800Ais st. PLs let me know this is ISP issue or IOS/ BRI card issue.

I have this problem too.
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Peter Paluch Tue, 07/28/2009 - 23:58


Personally, I would say this is a provider problem, according to the message "No circuit/channel available". For that message to appear, already some signalling must have taken place which means that the ISDN connection itself should be working.

Try using the command

debug isdn q931

to see the Q.931 signalling messages sent on your D channel. Maybe that will put more light into this issue.

Also, at least during the attempted call and shortly after it, the "show isdn status" should say that Layer 1 status is "ACTIVE" and Layer 2 status is "MULTIPLE_FRAME_ESTABLISHED". Can you confirm that?

Best regards,


Richard Burts Thu, 07/30/2009 - 04:54

If the router is generating this response:"Layer 1 Status:DEACTIVATED" then I do not believe that debug isdn q931 will be very helpful.

Are we sure that the router ISDN interface is connected to the right telco line? Are we sure that the telco line is active to an ISDN switch? Are we sure that the switch type configured on the router correctly matches the switch type of the provider?

And if I were going to look at debug I would start with debug isdn q921 to verify signaling before I used q931.



Peter Paluch Thu, 07/30/2009 - 07:29


I have personal experiences with ISDN lines that are not activated all the time but rather only on-demand when there is a call being placed. Between the calls, the line will be deactivated. Therefore, the output of "Layer 1 Status: DEACTIVATED" does not necessarily indicate a Layer 1 problem.

I originally thought that because of the error message that was posted earlier, some Q.931 signalization already took place (the 0x22 message "No circuit/channel available"). Therefore I suggested debugging the Q.931 signalling.

So I thought here that there is a problem with the telco so that's why I suggested going with "debug isdn q931". In fact, the q921 debugging is more related to the Layer2 initialization and I expected that to be workable.

So these were my reasons but I admit that I perhaps haven't tackled it from the proper side. Thanks for your suggestions!

Best regards,


Wilson Samuel Thu, 07/30/2009 - 07:01

Hi Anuradha,

1. Layer 1 Status:DEACTIVATED

The L-1 issue mostly is due to either faulty cable or faulty cabling somewhere between the NT-1 (if are not in the North America) and the Provider.

If you have got an ISDN Phone or any device (TA) then you may want to test the line with a phone call.

2. ERROR**: host_disconnect_ack: Call rejected cause No circuit/channel available(0x22) call id 0x800Ais s

Issue is being thrown possibly when you are trying to initiate an ISDN call (voice or data from the router) because the L-1 is not functional and the router doesnt see any ckts available for establishing any communications.

Hope that helps


Wilson Samuel

Richard Burts Thu, 07/30/2009 - 07:50


That is an interesting perspective. My experience with ISDN has been that if layer 1 was deactivated it meant a problem and no higher layer could work.

If the original poster is in an environment where ISDN may work on demand and that layer 1 is not always active then your approach makes sense.

In troubleshooting we sometimes start at the lower layers and work up. And sometimes we start at the upper layers and work down. For some circumstances one approach is perhaps better and for other circumstances the other may be better. Since my assumption was that the problem was likely a lower layer issue I started from the bottom this time. You assume that the problem is higher and start from the higher layer. As long as we work through the troubleshooting logically we should be able to find the problem no matter which method we start with.



chinkevi_2 Thu, 07/30/2009 - 16:50

hi Rick, this is true mainly in US where layer 1 will always be up.

a lot of ISDN switch in Europe will make layer 1 stay down if no traffic. The only way to test the isdn is to bring up traffic, layer 1 and 2 will kick in, and start dialing as normal.

as original post say no channel available after dial, and if layer 1 and 2 were up at the time, i agree the isp would need to be checked.


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