LPE wont sign in to Lync externally

The Problem

Lync Phone Edition (in my case Polycom CX500 and CX600) wont sign in to Lync from externally. Internally working fine.

The phone goes through the steps of finding the time server, then finding the Lync Server – OK. Then gets stuck on Signing in… Connecting to Lync Server
This also happened to the CX600 EVEN when pairing to my desktop over USB for sign in…

The Evidence

Checking the Lync Edge Server logs I found…nothing! Same as the Front End, also nothing!
Since everything else seemed to be working I started to wonder how the LPE’s are different from the desktop client.
Going through the motions of validating the DNS using the RUCT.exe tool I found that when I tried to test the port availability on selected records on the SRV record for -sip._tls I got an error stating that the host was not found.

What I found was very interesting. The SRV record for  _sip._tls.sipdoamin.com resloved to sip.sipdomain.com BUT the Public Certificate Common Name was LyncEdge.sipdomain.com with the name sip.sipdomain.com as a Subject Alternate Name.

The Solution

I changed the the SRV record so that the target was the published public name LyncEdge.sipdomain.com. Effectively this meant that the SRV target was also the Common Name on the Public Certificate.

The Common Name on the Public Lync Certificate should always be a resolvable target for the SRV records


About Paul B

My name is Paul Bloem and I am employed at Lexel Systems in New Zealand as a Principal Consultant for Unified Communications. I have been working on enterprise voice solutions for over 20 years. My first 10 years were spent working for a Telco in South Africa (Telcom SA). This is where all the groundwork happened as I was exposed to just about every aspect of telecommunication you could imagine. I develop an interest in PBX technologies and eventually became the go-to guy. Next, I had a 10 year run at Siemens South Africa, most of my time there was as a Technical Trainer. During this time VoIP hit the world stage, I had the privilege of introducing VoIP both as H.323 and later SIP across the Siemens HiPath 4000 solution stack. In 2008 I immigrated to New Zealand with my newly attained MCSE, I was ready to go where no PBX Techie had gone before. I was employed to explore OCS 2007 and that was pretty much the beginning of the end for me. I have been working on OCS and Lync ever since. My current role focuses exclusively on Lync and associated technologies.. That includes pre-sales, consulting, architecture and design, training and support. I even get to play in the development space from time to time - focus on play ;-) I was nominated as a Microsoft VTSP for Lync early in 2013 and also awarded Microsoft's MVP award for Lync in 2014.
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