fax comm error using T38 across H323 trunk

[bradley.huet]

I have a customer that has a CUCM 8.6 cluster with an H323 trunk all voice calls across this trunk work fine but we have an issue with one type of fax machine that returns a comm error when sending a fax. The actual fax send from this fax machine is received on the other end however.
The fax machines on the Cisco connect via an fxs port on an mgcp controlled gateway. On the AVAYA side the fax machines connect via an analogue port on the G250 gateways. The model fax machine that gives this problem is a cannon L120, we have also tried an L160 and that works fine.
The fax protocol I'm using is T.38.
Any ideas will be great.

[Harmit Singh]

Hi Bradley,

It sounds like despite the error seen on the fax machine, the fax still goes through fine to the other end. Is this a problem with one or all cannon L120 machines in your customer's environment? Did you try contacting cannon for them to send a technician to verify the fax settings? Is there an error code that accompanies the comm error?

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Regards,
Harmit.

[bradley.huet]

Hi Harmit

That's correct the fax is still transmitted successfully despite the error on the L120 fax machine. It's all the cannon L120 devices that have the problem. The error that comes up on the LCD is comm error 0001. The cannon technical guys have not been out as yet we are awaiting for someone to be despatched. However I have checked the fax machine settings which looks the same as what I have on L160 fax machines which work fine.

[Harmit Singh]

Hi Bradley,

Did you try reducing the fax speed to see if that helps? Is Error Correction Mode (ECM) enabled on the cannon L120 machines? Toggle this setting on one machine and test again. HTH.

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Regards,
Harmit.

[bradley.huet]

I have forced the speed of the fax machines down to 9600 from 14400 with no difference.
I will try turning on ECM on the L120 but do I turn it on at voice gateway level as well.

[bradley.huet]

I have tried toggling the ECM mode on the both the fax machine and the mgcp gateway, but I still get the same result.

[Harmit Singh]

Hi Bradley,

Considering that the error appears to be cosmetic in nature and that it's only happening for a specfic fax machine model in your network, I would say engaging the fax vendor is the best place to start.

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Regards,
Harmit.