Sending Fax from SPA112 works but....

[computer130]

There are two numbers which i always get the same error.

See the log here, i do not know how to solve this. I marked red what i think is the problem.

26.09.2017 10:43:45 - L:5084.1[Extn:310] got Terminated Send Req BYE from 0.0.0.0:0 tid=f32dff510fc66a01 [email protected]: BYE sip:[email protected]:5060;ref=310 SIP/2.0
Via: SIP/2.0/ ;branch=z9hG4bK-524287-1---f32dff510fc66a01;rport
Max-Forwards: 70
Route: <sip:[email protected]:5080;user=proxy;uri=sbc.f35cc1d9>
Route: <sip:[email protected]:5060;user=proxy;tnlid=sbc.f35cc1d9>
Contact: <sip:[email protected]:5060>
To: "Fax"<sip:[email protected]:5060>;tag=cb1f36cccb45d4o0
From: <sip:[email protected]:5060>;tag=186c1e73
Call-ID: [email protected]
CSeq: 3 BYE
User-Agent: 3CXPhoneSystem 15.5.3849.1 (3849)
Reason: SIP;text=Application Rejected Sdp(usually no common codec)
Content-Length: 0

Can Post the whole log if necessary

 

[leejor]

Are you using t.38?
Is the extension a FAX extension?
Is the call going over a provider that supports t.38?

I see 3CX Bridge mentioned, is that is fax call to another PBX?

 

[computer130]

Yes, the SPA112 seems to use t.38 and the provider supports this.
It is not a fax extension, because the 3cx is hosted at ovh. I used the 3cx SBC in the office to connect to the 3cx pbx in the cloud.

 

[leejor]

As I recall (and I may be wrong), T.38 will only work if you use a Fax extension. There has been some "movement" on fax over G711.
https://www.3cx.com/blog/docs/g-711-fax-functionality/
https://www.3cx.com/blog/docs/foip-fax-over-ip-t38/

 

[computer130]

I knew these links, but i thought this was only about fax receiving.....
But you may be right. Maybe T.38 only works on a fax extension. But i can't use Fax extensions, because the 3CX is not local, and Fax extensions can only be local.

Currently i asked the SIP Trunk provider if it is possible to use forking, so that i can register the trunk insider the FXS Gateway an keep 3CX away from fax sending. But i have no answer yet.

 

[us1]

Are you using any of the 3cx functions for faxing? If not, skip 3cx and register your ATA directly with the SIP provider. One less link in the chain and that is exceptionally important for faxing.

 

[sip.bg]

To use remote fax extension (ATA), you need a VPN to the remote location. It is not working behind 3CX SBC nor with STUN. Fax extension (ATA) must be a local extension. T.38 is supported only for fax extensions in 3CX.

 

[computer130]

Okay.
I know:
Fax Extension can only be local or VPN. Both is not possible with 3CX at OVH Cloud. So not Fax extension can be configured in 3CX when it is in the cloud.
Fax as a normal extension seems to not use t.38.

Only way to use 3CX in cloud is if the customer does not need fax, or it SIP Trunk allows forking, so that we can configure it directly inside the ATA.
3CX does not provide a email2fax solution so it is simple.

If customers need fax sending functionality, we do not offer 3CX in future.

Thx all for the help.