Call through gateway to Nortel phone w/Call FWRD set

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Jan 25th, 2008
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We have two PBX's. Our existing PBX is a Nortel Meridian which houses phones and is our tie to the PSTN. We have began the process of migrating phones over to our CM server running 5.2 We have a 3725 H.323 gateway that sits between the two PBX's - IOS v12.4(10c).

Call Flow - IP phone---CCM-->Gateway (GW)-->PRI-->Nortel---->ext.

When a user on the Nortel side places 'Forward all calls' on their phone to an external DID and someone from the Cisco side try's to dial the Nortel's extension they get a fast busy.

Please find the attached partial config and some debug. Any thoughts would be greatly appreciated.


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paolo bevilacqua Fri, 01/25/2008 - 13:08
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this is a bit strange to understand.

first of all, the router has two PRIs, not one like depicted above. And you mentioned two PBX, I see only one above.

This makes more difficult to understand what is connected to what

Then, the first call fails for no apparent reason, compare to last call "WORKING", only the called number and the channels are different, yet the router get a complain about an invalid IE, which one, I cannot tell.

Finally, the second failed call, a re-hunt of the first, also fails but because "Switching equipment congestion". Again, is not clear why.

Please clarify how things are hooked up to help us understand what's going on.

Jeff Thompson Fri, 01/25/2008 - 13:49
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Thanks for your reply. My appologies for not being clearer on my description.

So actually there are three PRI's that connect the GW to the Nortell PBX. When I mentioned two PBX's, I was referring to 1. being CallManager AND 2. being the Nortel.

The difference between the working call and the call that fails is the one that fails as been set to do a call forward (which is my issue). The reason the called numbers are different is I was capturing the debug remotely and TAC wanted to see that calls worked to extensions over on the Nortel side AND I was not physically at the location to turn OFF call forward on the nortel handset that I am using to test this issue.

so If I place a call from an IP phone to phone on the nortel side and the Nortel phone has been setup to call forward out to the PSTN, I get a fast busy

As far as re-hunt and failing because "Switching equipment congestion" I am not clear on this as well?? The call forward pattern setup on the Nortel handset is '96005418'. Do I have a dial-peer issue for when the nortel phone is redircting the call out to the PSTN?? At that point, is the gateway grabbing another channel which is messing up the call setup??

Rob Huffman Fri, 01/25/2008 - 14:05
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Hey guys,

Jeff, if the Nortel phone is forwarded to an Internal number does this call work? If so, I would look at the Nortel configs for a setting that allows/denys Trunk to Trunk connections. In many cases this is blocked to prevent Toll Fraud. The Nortel likely sees the CCM Route as External and as such is actually blocking this type of call.

Hope this helps!


Jeff Thompson Fri, 01/25/2008 - 14:16
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Thanks Rob. Great point. yes in fact it does work if forwarding to another extension.

paolo bevilacqua Fri, 01/25/2008 - 14:23
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Hi, I would check per Rob's advice first, that is very reasonable.

Still I'm puzzled by the difference in the clearing cause when router tries to re-hunt to the second trunk.

I would expected cause to be "call reject", not what we've seen. Anyway, ISDN stuff is know to do strange thing at times.


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