Patton SN4112 failing to create outbound lines

[steven.theck]

I want to start by saying I'm very new to the 3CX system (just installed over the past week), but I have been able to troubleshoot all of my issues on my own until now. So I thought I'd ask the community in case someone else has experienced this before I contact a 3CX partner, since many places are currently closed in my area due to the COVID-19 situation.

I am running version 16.0.507 on Windows Server 2019 with Yealink T48S phones and a Patton SN4112 FXS to connect our analog fax machine for outbound faxes. We have SIP trunks with Comcast Business. Prior to switching to 3CX, we were using an Avaya IP Office IP500V2, and all incoming/outgoing calls and outgoing faxes were handled through the IPO with the same SIP trunks. Faxing over SIP wasn't always reliable (as others have expressed on the forum), but it did work most of the time.

I followed the guide here to setup the SN4112, and after some DNS issues, I was able to get it connected to the 3CX and the extensions appear as registered under System Extensions. When I have tried to send an outgoing fax though, the activity log gives the following message every time:

03/25/2020 1:11:26 PM - : Failed to create outbound lines to call 18884732963
03/25/2020 1:05:29 PM - : Failed to create outbound lines to call 18884732963
03/25/2020 12:59:24 PM - : Failed to create outbound lines to call 18884732963

And the call log shows the following:

03/25/2020 1:11:31 PM Fax (3701) 18884732963 00:00:35
03/25/2020 1:05:34 PM Fax (3701) 18884732963 00:00:37
03/25/2020 12:59:28 PM    Fax (3701)    18884732963    00:00:47

I currently don't have an analog phone (aside from the fax machine) to test the line with, but the calls do sound like they are connecting (fax tones coming from the fax machine).

I believe Comast supports T.38 over SIP, but I have tried setting the fax transmission mode to G711A as well with the same results.

Sorry if this isn't enough information, but I'll do my best to provide any additional information that is necessary. Thanks in advance for the help!

 

[cobaltit]

Congrats on getting your setup this far! And as far as partners go, we are still open, but I don't think you need one just yet.

I think the first thing to do is check the 3CX activity log to see if calls are hitting 3cx and then going out the trunk. The latest call log (presumably from the Patton) shows a length of 47 seconds which would seem long enough for a fax to go out.

 

[steven.theck]

Thanks for the quick reply @cobaltit. All I'm seeing in the activity log is "Failed to create outbound lines to call", which appears in the logs before the fax transmission signal comes through on the other end. The Patton does show that the line is connected through the entire duration of what the call log shows, but there's no additional logs in the activity log.

I've been testing out a few different things, and I made a test call from the fax machine to my mobile phone. The call connected, and I was able to hear the tone from the fax machine (HP MFP M479fdw) and my voice from my cell was coming through on the fax machine. So it appears that the call does connect, and I'm now thinking it may be an issue with the fax machine not recognizing that the call is connected, therefore it isn't attempting to send and times out.

 

[cobaltit]

That's a possibility. Many sites recommend turning the speed down on the fax machine or turning off ECM. For the record we only do incoming faxing via 3CX. We don't support outbound faxing via ATA through 3CX. If you insist on going that route you are better of bypassing 3CX and trying to go directly to your SIP trunking provider to the ATA. For our customers we use a store and forward ATA which just works.

 

[steven.theck]

The MFP is set at 9600 bps, and ECM is turned off. I'll probably play around with it a bit more, and if not, I may be contacting you about the store-and-forward ATA solution.

Thank you for your time!

 

[eddv123]

Failed to create outbound lines

As you have been doing already pin-pointing where the issue lies is the most important first step. It sounds initially to be either an issue with the trunk or outbound rule on 3CX however I would use the following to prove this.

Run the system in VERBOSE logging mode and use the binary log viewer to identify whether the issue is within 3CX - its very detailed and very straight forward: https://www.3cx.com/docs/3cx-log-viewer/

Wireshark is also useful to see what messages are being sent (you can see SIP and the T.38 fax messages) I have used this several times when troubleshooting issues with FAX. https://www.3cx.com/docs/capture-network-traffic/

FYI also, Patton gateways have excellent troubleshooting capabilities if you login to the device via CLI and run the following command-set it could provide some useful information (especially in regards to the settings on the local FAX):

enable
debug call‐router
debug call‐control
debug fxs
debug media-gateway control
debug media-gateway fax-data
debug context sip‐gateway signaling detail 5
debug context sip‐gateway transport detail 5
debug context sip‐gateway error

Replicate the fault and when finished enter no debug all to remove the tracing.

 

[steven.theck]

@cobaltit @eddv123 I finally got the outgoing fax issues resolved. It ended up being a combination of things. I set the audio codec on the Patton to G711U, I setup the Patton as a regular phone extension instead of a fax extension in 3CX, and moved the G711U codec to the top of the list in the phone provisioning tab for the extension. After these changes, I was able to send a fax on the first try.

Thank you both for your help!

 

[cobaltit]

Great, thanks for the update and happy faxing!

 

[eddv123]

Just as an FYI for future issues, if this is/was an issue with codec mis-match between provider you may of seen in a Wireshark capture a 488 not acceptable here maybe the response you see coming back from the provider.