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Incoming calls from PSTN keeps failling


If anyone could help on this one it would be great.

Our incoming calls from the PSTN keeps failling. Incoming/outgoing calls across the WAN does work, and outgoing calls across the PSTN also works fine.

We use MGCP gateways.

A show isdn stat shows layer 1 is active and layer 2 is established.

sho controller e1 shows no errors

debug isdn 931 cant pick up any of the incoming calls.

The service provider said theres nothing wrong on their end. THey can see the PRI's are up, and that they are sending the calls to us but they dont get answered.

Any ideas what could cause this?

Im thinking of resetting the MGCP, but obviously only after hours to see if this could resolve the issue.

No changes were made recently, and everything was working fine before the weekend.

Any help would be much appreciated.           


Incoming calls from PSTN keeps failling


Since debug is also not giving any output I think restart or router will help you. I cant see any other issue which may affect it.


Ronak Patel

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Regards Ronak Patel Rate all helpful post by clicking stars below the answer.
Super Bronze

Incoming calls from PSTN keeps failling

Hi Eugene

If you are able to make outgoing calls then the circuit is functional.

If you don't see output in debug isdn q931 for an inbound call, this typically means the call is not reaching your gateway at all - i.e. it's a service provider issue regardless of what they say.

You can certainly try resetting the GW, but int the meantime I would keep pressing your service provider. It could be an issue with your gateway/IOS in theory but in my experience the q931 debug is pretty reliable if the circuit is up.

If you have the equipment connecting an ISDN tester to the circuit is the best way to prove these things.



Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!
New Member

Incoming calls from PSTN keeps failling

So I didnt do anything, and now all of a sudden it all works. I suspect that the SP did something, but they keep telling me they havent done any changes on their end. But Im giving you both a good rating, because my next step would have been to restart the MGCP service on the gateway.

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