Fast busy when calling extensions in same CSS

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Oct 15th, 2009
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We are getting a busy signal when dialing from an IP phone to a FXS port. The extension numbers 80XX are in the same calling search space, does anyone have any ideas on what to research? We have changed the CSS classification between the FXS ports to see if that made a busy. Could it be the router causing the busy signal. TIA - Thomas NH

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Chris Deren Fri, 10/16/2009 - 08:36
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CSS on the GW has nothing to do with inboud calls, here is what to look for:

Is this MGCP or H323 controller FXS port? If MGCP make sure the DN is assigned to proper parition

If H323 make sure you have matching dial-peers on the GW pointing to the FXS ports.


Brav3h3art Fri, 10/16/2009 - 12:21
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Hi Chris -

Its MGCP and all extension are in the same unique partition. I'll check the dial-peers on the router again. What I do not understand is, it's an intermittent busy on FXS ports? If I dial from an IP phone to an IP phone in the same DID range (partition)the phone rings OK, but if I dial a FXS port in the same DID range (partition) I get busy tone. I have done 10 Nortel to VoIP conversion this year and have never seen this problem ever. We are running CUCM 6.12 and have several sites out there with almost same setup, but do not have these types of problems. I wonder if it has anything to do with the OSPF? I am open for anything - Thanks Thomas NH

Brav3h3art Fri, 10/16/2009 - 13:16
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That issue is related to CLID on outbound calls, we are OK there. We are passing the External Phone Number Mask with no problems on the PRI T1s. This problem is within the partition itself and is a major problem. Mainly my project is in jeopardy from being cut over. Any other ideas...TIA-ThomasNH

Nicholas Matthews Fri, 10/16/2009 - 13:44
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debug mgcp packet

debug voip ccapi inout

debug vpm signal

on the fxs gateway.

"I call and get busy tone" can be literally a hundred things.



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