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Is Faxing over SIP available in UC500/CCA?

Hello All,

Is Faxing over SIP available in UC500/CCA?

We are proposing a UC560 solution for a client who currently uses a "Fax Press" for faxing over a PRI to their Server.

We are suggesting SIP Trunking because they expect to add phones and users thus increasing the call volume.

Does Cisco have now or have plans soon for T.38 faxing over SIP?

Please add your thoughts and answers.

Thank you, Paul


As far as I know the system does not currently support T.38 termination (though I believe it is able to pass T.38 traffic).

Fax over SIP using G.711 works well in my experience... IF and only IF there are not latency/loss/jitter issues with your internet connection. We have some people who have been using it for a long time with no issues, and others that go from working to 100% failure overnight due to ISP issues. (all this is of course assuming you are talking about SIP over the public internet)

I can't speak to Cisco's plans for the future. However you might want to check CME... UC500 is based on CME but is usually a few versions behind the latest CME release... if it exists in a newer CME, it will almost certainly be added to UC500 at some point.



I recently went through the process of setting up T.38 and got it to work:

Let me know if you need help.



My mistake apparently! I was under the impression that T.38 was not supported... its wonderful to hear otherwise.

I will have to give this a try.

Thanks Brett.


HI Brett,

Is there any way you could send me the configs you used to get this working or help me.

We have a client with a UC560 at HQ with SIP comming in, a 2nd site is linked through a SR520 and leased line as a teleworker site. a 3rd Site is a UC540 connected via the internet and Multisite VPN.

All incoming calls for all sites com in through HQ.

We have to get a fax to work on the UC540 in site 3.

And a fax to work in Site 2, we setup a VG202 in Site 2, the franking machin there can dial out and update itself, but an outbound fax doesnt work.

Yesterday I manged to get incoming faxes wokring to Site 2 but they are working on G711, not T38, thouhg it was an attempt to add the T38 that got the incoming working.

any suggestions you can make or even let me see the lines in your config that deal with the T38 and faxing.





I realize I should clarify something, this is a pure CLI config.  You can't do this from CCA.

Anyway in CLI:


Config t

Voice service voip

Fax protocol t38


No sip-profile 1000




As for the "No sip-profile 1000" line, this was because I found that CCA (I assume because I didn't put it there) put in a SIP profile 1000 that was stripping out a required SIP header.  You might not need this. 

The otherwise, you also need a SIP provider that supports T.38 if you are going to be faxing to anybody outside of your system. 

I'm not sure how this specifically would work with your Site 2.  Is all phone service to Site 2 via the VPN to Site 1? Is the fax machine at Site 2 analog?  How is it currently connected?

Anyway, this is a start anyway.


Rising star

Hi All,

Just be aware if you do the above CLI config it will put your system out of scope, if you cannot do it in CCA and you are not UC-Express Certified then you are pretty much on your own (In theory).

However the UC-500 supports Fax over SIP or "FoIP" quite well, its tolerance level is reasonable or much better than say the Linksys PAP devices and I have seen it operate for a while with only minimal issues, although there have been the occasions where it wouldn't work at all and just give heaps of grief.

Remember if you cannot do something in CCA and you are not certified for CLI work around's, then avoid selling the solution and try and keep the system away from it, it could cost you the deal



Cheers, David Trad. **When you rate a persons post, you are indicating a thank you or that it helped, but at the same time you are also helping to maintain the community spirit - You don't have to rate posts and you wont be looked down upon :) *