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New Member

Fax success on ATA?

I know the Cisco ATAs (186 & 188) support faxing through G.711, potentially also with passthrough configured on CME, but can anyone provide comments on their experience doing this?

Is it easy enough to attain 14.4kbps speeds on the fax?

We're looking at using ATAs to replace some POTS lines in a small office. The ATAs will be on the same LAN as CME and will be sending and receiving faxes via two BRI ports on the CME system (2801).

I'm looking more for comments on how well it works rather than pointers to documentation on how to do it. (which I already have)


Re: Fax success on ATA?

Generally fax over ip is not very reliable when going over FXO POTS lines. You may need to play with the gain and output attenuation settings to make sure audio is loud enough on the fax machine and that there are not any echo. Also superG3 is not supported with ATA because it uses v.34 modulation and ATA does not support modems.

This URL should help you:

New Member

Re: Fax success on ATA?

Thanks for the feedback. We're not trying to run superG3 or any such weird crap, and all traffic will be contained within a QoS-enabled LAN. I'm hoping I'll be able to get away with this, specifically with the newer version of the ATA186 which has improved support for faxing.

If all else fails, we'll at least have an ATA we can use old POTS phones with.

New Member

Re: Fax success on ATA?


i have tried the ata with isdn bri and that works fine, but analog lines is a bit unreliable maybe...

PS cme 3.4 and less doesnt support fax when using ata as a device like a phone (sccp), you must use a h323 dialpeer to get fax working (bug :o(

just a tip...


runar iversen

New Member

Re: Fax success on ATA?

We'll be using BRI so I'll see how it goes.

That's a sneaky bug... thanks for the advice.

Re: Fax success on ATA?

I'm probably way too late with this reply. ;-)

We actually run dozens of faxes with ATA boxes and have very few problems.

(not all fax problems are ATA problems).

The other guys are right: no speedy faxes, ...

QoS is important - if there is a problem in the network you will have fax problems, no question.

We also use successfully some 2801 with BRI and ATAs.

Be aware that there is a clocking bug CSCeh42852 which is *bad* for faxes. (the text is weird in the bug notes, but that's pretty normal)

Just use 12.3(11)T7 or later to get around this one.


New Member

Re: Fax success on ATA?

I'm still in the process of having the order approved, so this info is at least comforting - thanks.

I also ensured we're ordering the newer revision of the ATA186's. (-I2-A)

Re: Fax success on ATA?


Verify region setting is using G711 codec


Config t

Voice service voip

modem passthrough nse codec g711ulaw

dial-peer voice XXXXXXX voip

modem passthrough nse codec g711ulaw


If you add the above then change the ATA (http://X.Y.Z.A/dev)

Audio Parameters

LBRCodec to 0

AudioMode 0x00150015 (default is 0x00350035)

ConnectMode 0x90000400 (default is 0x90000400)

New Member

Re: Fax success on ATA?

Is this only for h.323 ata or for SCCP as well?