Wednesday, April 20, 2011

Troubleshooting Lync Edge 101

We installed a "simple" Lync Edge system with collocated Front-End and Mediation server and Enterprise Voice connected to the PSTN via a Nortel CS1000 PBX.

After configuring (among other things)
  • Internal DNS
  • External DNS
  • Routing on the EdgeServer
  • Internal Certificate
  • External Certificate
  • Public IP addresses
  • Primary DNS suffix on the EdgeServer
  • Open ports on the Internal Firewall
  • Open ports on the External Firewall
  • The mediation server to find the PBX
  • The PBX with a SIP Trunk
  • The topology, exported it and imported it on the EdgeServer
  • Users with external access, enterprise voice and a valid line URI
  • A Voice Policy, PSTN Usage and Route
  • Automatic login internally and externally
and checking the configuration a few times, we could call…

External Lync <---> Internal Lync
Internal Lync <---> Mobile Phone

But not…

External Lync  ---> Mobile Phone
Mobile Phone  <---  External Lync

The signalling from the External Lync client to the Mobile phone went through, the phone would ring and we could answer the call. On the external Lync client the status shifted from "Calling" to "Connecting call", where it sat for a few seconds and finally displayed "Call failed due to network issues". This indicated that the signalling path were working fine and the problem was happening as the system tried to setup the media stream.

We then used the Lync Server 2010 Logging tool to find this error message:
"Call failed to establish due to a media connectivity failure when one endpoint is internal and the other is remote"

Which led us to this post on the Lync forums: Incoming PSTN call to external user fails to connect

After investigating the logs some more we saw that the mediation server tried to establish a media path straight to the external client!? Did it not know we had an edge? - No, it actually did not!

After looking in the Lync Control Panel / Topology / Standard Edition / Mediation Server, we noticed that the EdgeServer setting were "Not Set"

With Power Shell we could check this with the following command:

Get-CsService -MediationServer

Identity                 :
Registrar               :
EdgeServer            :
SipServerPort         : 5070
SipClientTcpPort     : 5060
SipClientTlsPort      : 5067
AudioPortStart        : 49152
AudioPortCount       : 8348
DependentServiceList : {PstnGateway:}
ServiceId             : 1-MediationServer-4
SiteId                 : Site:Stockholm
PoolFqdn             :
Version               : 5
Role                   : MediationServer

Also, in the Lync Control Panel / Topology / / Edge Server / Dependents, we could only find “Registrar:…” and “ConferencingServer:…” and no "MediationServer:....

So our Mediation Server did not know we had an Edge, and the Edge server did not know about the Mediation server. My guess is that internal calls to PSTN worked simply because the Mediation server were collocated with the Standard server.

However, we used the following command to make things right:

Set-CsMediationServer -Identity "" -EdgeServer

And after restarting the Lync control panel it displayed correct data, and calls from the external Lync client via the collocated mediation server to PSTN worked (and the other way around as well!)



  1. I'd been puzzling about exactly this issue for weeks - many thanks for working this one out as we were miles away from a fix.

    I can confirm this resolved our issue after re-starting the mediation service on a lync server where mediation was co-located

  2. Hi!

    Happy I could help! I have seen several people facing this same issue.


  3. You just save my time, thank you very much.

  4. Hi i happen to stumble upon your blog after months of searching. My company was unsuccessful integrating the CS1000 Avaya PBX with lync so much so that we have ordered Avaya's ACE Server(Which i am not thrilled about). Please is there any info you can send me about how to successfully integrate Lync to this PBX. this info would be greatly appreciated my email address is or Thank you.

  5. Hi Eddison,

    Unfortunately I have no practical experience on Avaya ACE and Lync. OCS and MCM worked fine, but ACE is a different animal i suppose. What I can offer is this:


  6. A thousand blessings on your house!! This one was killing me.

  7. Bingo!
    That did it!

  8. I had the exact same problem as described. Thanks for the information!


  9. Thanks man, had the same problem, that saved my weekend. I think this was caused by some CU in the past few weeks