Phone ATA187 not working with fax and DTMF

[jfernandorosa]

Dear Experts.

I have a problem with cisco ATA187 and SIP ISP, DTMF and Fax not working together.

Scenario:

CUCM9.1 -->ATA187 --> SIP TRUNK -->CUBE-->SIP ISP.

ATA187 -> DP-G711 -> MTP SIP TRUNK uncheck -> Fax ok -> DTMF no ok.

ATA187 -> DP-G729 -> MTP SIP TRUNK check -> Fax no ok -> DTMF ok.

ATA187 -> DP-G711 -> MTP SIP TRUNK check -> Fax no ok -> DTMF no ok -> Call Problem.

I need the dtmf and Fax working together.

Thanks for help!

John.

[jfernandorosa]

Other IP Phone models work well! 7911, 7942.

[Jorge Armijo]

First of all, you need to know what Fax Protocol your Service Provider uses, usually is t.38. Second, is well know that MTP causes several issues with Faxing, if the tones are sent on the RTP stream. If you need to have MTP on the SIP Trunk, you need a HW MTP on Cisco IOS Router with codec pass-through configured. Also, you may want to have g711 for fax calls, otherwise they will fail.

HTH

--
Jorge Armijo

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