H.323 Gateway Call Forwarding to Cell Phone Issue

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Apr 9th, 2009
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I have a site that is using an H323 GW that is configured to use a CUCM 6.0/Unity 4.0 cluster. There is a 1MB line on the gateway for incoming calls which forwards to an AA on the Unity server. Normal inbound and outbound calls work fine. However, if a user forwards their Cisco IP phone to their cell phone it fails:

The auto attendant tells you “wait while I transfer your call” and then you hear 3 beeps. The user's cell rings once and then the call disconnects on the user's phone. The call stays connected on the caller's phone.

This is a new setup with h323 so it probably something simple.

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CHRIS CHARLEBOIS Thu, 04/09/2009 - 10:27
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I think I've seen something like this before. You need to define a Media Termination Point and associate that with a Media Rersource Group and MRG List, and make sure that the device pool that includes the voicemail ports is assigned that MRGL. At least, I beleive that is the case. It has to do with hairpinning on a H.323 Gateway.

gmgarrian Thu, 04/09/2009 - 11:31
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Okay, in CUCM I set the gateway config to use a MRGL and to require a MTP. Now when I call the 1MB and get the AA I can dial the extension, it says "wait while I transfer your call..." then there's about 1-15 seconds of silence. After that a recording says that the extension is not available and to leave a message.

Is this a problem with Unity?

CHRIS CHARLEBOIS Thu, 04/09/2009 - 11:50
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I assume that the calling search space is configured correctly. I doubt you would have received the single ring you were getting before if it were a CSS problem. Did you perhaps modify the cell number within Unity during your troubleshooting to something that isn't valid?

gmgarrian Thu, 04/09/2009 - 11:51
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Unity is set to ring the extension, and the extension is configured to forward calls to the cell number via CUCM, not Unity...

CHRIS CHARLEBOIS Thu, 04/09/2009 - 12:01
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Can you call the extension directly and forward it to the cell phone? And verify the configuration by forwarding it to another internal DN to make isolate he problem to calls forwarded to the PSTN.

gmgarrian Thu, 04/09/2009 - 12:13
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Everything's been tested, the calls only fail when dialing in via the 1MB line on the H323 gateway.

CHRIS CHARLEBOIS Thu, 04/09/2009 - 12:24
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OK, let me take a step back here... You have a 1MB analog line coming into a VIC-FXO port on the H.323 router, yes? You call in on that line, Unity answers, sends the call to the CUCM extension, which is configured to CFAll to a cell phone number... I assume you have some other PSTN access to allow the call to get out to the cell phone, right? Or does the 1MB line support mulitple calls in a trunk; I am under the impression that a 1MB is simply a metered 1FB, which support only a single call.

gmgarrian Thu, 04/09/2009 - 12:43
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You are correct in the call flow. The 1MB line is for single calls only. Outbound calls use a SIP trunk to the provider's network.

CHRIS CHARLEBOIS Thu, 04/09/2009 - 12:58
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So, the issue only comes up when an analog call from the PSTN comes into a H323 gateway which connects to an IP-based AA and then gets forwarded to a SIP provider. So the real problem has to do with the analog-to-SIP hairpinning within the gateway. I was assuming we were talking about analog-to-analog hairpin.

Can you see the call toward your SIP provider within the gateway via debugs? I'm not familiar with SIP trunking from H323, so I don't know what debug commands would be best.

Rick Arps Thu, 04/09/2009 - 12:33
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We encountered this issue when we had the gateway setup for fast start and the CM setup for slow start. Make sure these are consistent.



gmgarrian Thu, 04/09/2009 - 12:56
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Making changes based on that article would affect all calls, this issue in only for a specific scenario.


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