3cx Fax issues with a Cisco 112 ATA

[Brendan]

Hi everyone,
I'm having issues with faxing using the t38 codec from my cisco 112 ata.

basically the story is this. the ATA works 100% flawlessly on it's own, directly connected to the sip provider using the t38 codec, however, when connected to a fax extension in 3cx.

The call flow is as follows.
Starts up the call using g.711, re-negotiates to t38. as soon as it re-negotiates, my ata sends a t38 no signal indicator.

The outbound party receives 3cx's request to switch to t38, switches over and starts sending the no-signal indicator of its own back. it sends a V21-preamble back to 3cx, then sends a cng message etc.

It tries this over and over, however in the wireshark capture, all of these messages go to 3cx, and are never forwarded through to the ata.

Eventually the endpoint fax gives up as it isn't receiving anything back, sends a bye request to 3cx, 3cx acknowledges the bye and ends the call. no transmission ever occurs.

I'm using the latest build of 3cx with the in-built fax server with g.711 fallback for the fax server.

I just don't understand why 3cx is not passing through the data.

Both my trunking provider and the ata support t38 as like i said it transmits perfectly if i connect the ATA directly to the trunk.

Is anyone able to shed any light on this?
has anyone had a Cisco 112 ata work for outbound faxing using the t38 codec from a fax extension?

Kindest regards,
Brendan

 

[ivank]

Hello, Brendan.
Can you please set log level to Verbose and also set system parameter FAXLOGGINGLEVEL to 3, then repeat the fax call, zip 3CXIVR.log and send it to me?

 

[Brendan]

i have already set faxlogginglevel to 3 as i've seen in other posts and log level to verbose. i'm not at work atm but i can remote in and get this information for you it will be a few minutes.

I've uploaded the wireshark flow for you in the meantime to see if you confirm what i've been saying.
thanks

 

[ivank]

Looks like it has nothing to do with the 3CX FAX service at all.
You're trying to send a fax, and 3CX FAX works only for inbound faxes.

The reason nothing works lies in the provider: it doesn't respect RTP port change on re-invite:
- when g.711 is negotiated, PBX port is 9034;
- when T.38 is re-negotiated, PBX advertises (new) port 9036 (this behavior cannot be changed).
But provider keeps sending to the 9034 which is closed now since they decided to switch to 9036.
You can check this yourself by following calls with number 07-----379 in your capture.

So one thing you could try is to make Cisco advertise T.38 in the initial offer.
I'm not sure if this can be done, you need to check the ATA's Web UI & manual.

Hope it helps!

 

[Brendan]

thanks alot ivank i will look into it, much appreciated, i spoke with the provider at some stage and they mentioned something along those lines as well. definitely will look into this again.

 

[jbryant84]

I beat my head against the wall for HOURS on this. In my case it wasn't a provider issue. Once I changed the Fax Passthrough Method parameter to Reinvite under Line 1 settings in the WebUI of the SPA112 I was able to send. Also T.38 needed to be enabled on the right column on the same page.

 

[Brad Cann]

whilst i understand that 3cx has a i guess "Partnership" with welltech for fax ata's, it would be nice if they included setup details for other ata's which do the same thing, especially the cisco/linksys variety as they are common, cheap and readily available in most countries. I understand that the cisco ata's used to be supported and are now not supported for whatever reason, however many people use them because they are cheap to get and i assume the info used to be on here somewhere but now is not. i ran into similiar trouble when i setup the spa122, but found the info outside of the 3cx pages and was able to make it work.

 

[Chris ODaniel]

whilst i understand that 3cx has a i guess "Partnership" with welltech for fax ata's, it would be nice if they included setup details for other ata's which do the same thing, especially the cisco/linksys variety as they are common, cheap and readily available in most countries. I understand that the cisco ata's used to be supported and are now not supported for whatever reason, however many people use them because they are cheap to get and i assume the info used to be on here somewhere but now is not. i ran into similiar trouble when i setup the spa122, but found the info outside of the 3cx pages and was able to make it work.

Do you have yours working on 3cx 15.5? Can you share a link to the info you found?

 

[leejor]

Did you go through some of the other forums?

https://supportforums.cisco.com/discussion/11556131/spa112-fax-settings-1-line-or-2
https://supportforums.cisco.com/dis...12-t38-sending-fax-fails-receiving-works-fine

Obviously this deals with another PBX, but it is the SPA settings you want, and they should be the same for all servers
http://www.asteriskpbxsystems.com/cisco-spa122-fax.html

https://www.k2systems.ca/helpdesk/knowledgebase.php?article=137

There are a number more, if you do some Google searches.

 

[Chris ODaniel]

Yes, I do know how to use Google. No, I did not find an answer. I think the new fax server feature on 15.5 is hijacking my incoming fax. Is there a way to disable?

 

[sip.bg]

Cisco ATA like SPA2102, SPA8000, SPA112, SPA122 are simply not working reliably with T.38.
Replacing with Patton or AudioCodes will do the job, even with Chinese brands like Gaoke.

Cisco ATA can be used with Asterisk where T.38 is terminated by PBX itself and communication with ATA is G.711a/µ based (T.30).
3CX is passing through T.38 from the provider to ATA to handle, or terminates T.38 in case fax-to-mail is used.

 

[Brad Cann]

Do you have yours working on 3cx 15.5? Can you share a link to the info you found?

Have you updated the firmware on the spa, as the latest firmware does have multiple fixes for the spa112/122 for t.38 support. We don't send a huge amount of faxes, but the girls out the front haven't whinged at me. we also don't recieve a huge amount of faxes, but we use 3cx to pdf them and email them to our receptionist who onforwards them to whoever they are destined for. I'll try to find the link i used to configure the spa and put it in here when i find it.

Look i couldn't find the specific link, but i uploaded a screen dump of our ata on line 1. specific things marked in red. Make sure to use a high quality codec (IE 711u/a) and enable the options in red. NOTE: This is for sending OUTBOUND faxes as 3cx handles our inbound and pdf's/emails them.

our ata is running 1.4.1 (002) firmware.

Let us know how you go.