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I want to force a fax to run at 7200 instead of 14400

I have one fax attached to my H323 gateway ( cisco 3845 running 123-14.T 5 IOS) that gives errors if the speed is above 7200, if the fax comes via the voip network then it is ok as we are running g729 to that site so the fax rate is 7200, but hairpinned calls from the PSTN runn g711 come in at 14400. I cannot find a command that will force the fax to run at the slower rate,

anybody any ideas

3 REPLIES
Blue

Re: I want to force a fax to run at 7200 instead of 14400

I am assuming the call is coming in on a PRI (or CAS)on the same router as the fax. I also assume you don't want all local calls to use G729 -- just the fax.

You could force the call setup to be handled by the Call Manager rather than letting the router send the call directly to the POTS peer. You will also need to set the gateway to use MTP (assumes no Xcoder/MTP resources at the fax location). This will hairpin the call through the central site, and force it to run 7200.

You will need to assign the fax port POTS peer a bogus number, and do a called number translation in the Call Manager route pattern.

As an example, if your fax has a DN of 6500 you would have a VOIP peer with a matching destination pattern pointing to your subscriber. The CCM route pattern would translate that to *6500 and send the call back to the router gateway. Your POTS peer would have destination pattern of *6500.

You could use a different DN (that won't match the VOIP peer)rather than prepending the *, but it depends on your dial plan, and which you prefer.

Of course it may be simplier to find out why your fax machine won't run at 14400. That is unusual.

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Re: I want to force a fax to run at 7200 instead of 14400

sorry for delay in responding, I force the call to go via the Callmanager but still hairpins at the gateway, I created a route pattern on the Callmanger for ext 5785, which gets translated to 5685 which is the fax number on the gateway. the call comes in to 5785 the signalling goes via the callmanager, which then contacts 5685 at the gateway,when the call answers it will then hairpin at the gateway, how do you force it to use an MTP??

Blue

Re: I want to force a fax to run at 7200 instead of 14400

In the Call Manager H323 gateway configuration select Media Termination Point Required. If your MTP resource is as your central site this will force the call to use G729 and fax relay at 7200.

Please rate helpful posts.

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