Installing Microsoft Lync.


So I've read a lot of articles about installing Microsoft Lync, and desided to go for it. I only need the messenger part (calling from pc to pc with video). I do not need the IP/SIP telephoni part of Lync. My problem: It works fine internal. But external users can only write to each other. When they try to call, the user recieving the call, cannot answer it, and gets a "network error", when he clicks the answer button.

I have followed this guide:

And one thing that you should know. I have only install Lync on one server. Not 2. I have a dedicated public ip for Lync, where I can forward the traffic to the lync server throug a Cisco Asa 5505.

Any ideers ?


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Cliff GaliherConnect With a Mentor Commented:
There is documentation for a consolidated edge, but three IPs is definitely preferred.
Did you forward 443 and 5060 to the ip of  lync server ?
melfaritAuthor Commented:


TCP 80,443,444,5061,50000-65000
UDP 3478, 50000-65000

Windows Firewall on Lync server, is for the time being, disabled.


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You could try and use WireShark to see if the traffic is working as expected, this may help you see where the issue could be occurring. It does sound like a firewall or NAT issue, have you tried another router instead of the Cisco ASA by any chance? I know a data center that had some issues with the Cisco ASA's but cant recall if it was with MS Lync or something else.

Maybe try a SonicWall / WatchGuard or Draytek just as a test.
Cliff GaliherCommented:
Lync needs an edge server for external users. ALL Lync traffic is SIP, not just telephony features. And SIP as a protocol is not NAT friendly. No amount of port forwarding will solve this issue. You need an edge server.
melfaritAuthor Commented:
Hi Cliff,

Tnkx for the comment. I'll go ahead and install an Edge server. Is it really necessary to have 3 public addresses for this project?

Honestly, I have installed many exchange servers, and a lot of other microsoft and Cisco stuff. But I have NEVER seen anything so complicated as lync. Never...


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