Failing in SIP address on CUCM receiving a call from Skype for Business Server.

[rodmont74]

Hi, I am working on learning more between SIP trunks between CUCM 8.6 and 10.5 company Q/A env by doing a home lab. It is a basic Skype Server 2015 with two front end servers, mediation server (and SQL, file server, AD, cert server, etc... behind it). I am able to place calls from Cisco to Skype server having called number on E.164 and extension 2003 normalized to E.164 ( +55 21 5555 2003). For now, there is no partitions, device pools, CSS, etc... to start a simple calling scenario.

Issues happens as calls from Skype client are not able reach Cisco phone. Cisco translation pattern will make an E.164 into 4 digit extension as usual. The issue seems to be having SIP URI such as +552155552003@cucm.lab.inc instead of E.164 number +552155552003 coming to Cisco.

In my company Q/A environment, RTMT SIP trace shows only incoming E.164 so this looks like a misconfiguration in Skype server trunk. Just wanted to check if someone has already met this before and just by chance was not a CUCM trunk configuration mistake I did.

Thank you very much.

[Jonathan Schulenberg · Accepted solution]

Have you set the the Cluster Fully Qualified Domain Name as cucm.lab.inc and the Organization Top-Level Domain of lab.inc under System > Enterprise Parameters? If CUCM receives a SIP URI in the RFC3261 format of 552155552003@cucm.lab.inc instead of RFC3966 format of tel:+552155552003 it will Routing of SIP Requests in Unified CM.

[rodmont74]

Thanks for the explanation, Jonathan. I haven't changed them from the blank standard, but I am certainly behind on reading both RFCs and the Cisco doc you linked! Since we will run v10.5 and 11 later this year and I wanted to understand any differences in Cisco might have on SIP trunking, I have setup a new 10.5 and upgraded to latest 11 version, and rebuilt the trunk and phone and other elements for the test. On CUCM 11, it worked right from clean installation (upgrade from a clean 10.5.2 to be exact). 

Since I ruined my 8.6.2 days ago, I will have another one built, make sure I can call Skype server again and try Enterprise Parameters change after reading the Cisco doc you suggested. The reason why v11 works right away might be caused by Cisco improvements in SIP behavior in CUCM. I'll comment how it goes once I learn more.

Thanks.

[rodmont74]

Jonathan, organisation name, domain name (main) corrected this. Thank you very much.

I found my built Q/A env. in company is set up like this on v8.6.2 which makes sense, I just didn't know about it before. Once I am working on Lync/Skype provider, I will find out more if called entity could be set up as tel: on their SIP trunk, just curiosity.