Lync to Lync calls not working when users outside of network. But calls from Lync to external numbers do work.

Question

Hello,
We are having the following issue: when our lync users are outside of our network, just connected to their home internet or a public WiFi  and not on VPN, they cannot place calls to other
Lync users inside our network. They get a poor network connection message on the call window. But they are able to make calls from Lync to external numbers without a problem.
Inside our network, Lync to Lync calls work perfectly fine, the same for calls from Lync to external numbers.
Does anybody know what could be the cause of our issue? Perhaps I'm missing a setting on our Edge server. What should be the first thing I should check on my Lync servers?
Thanks for any help!

Answer 1

Have you opened up ports on your firewall from your internal clients to the edge on UDP/3478 and TCP/443?  This sounds like you might have a problem there.  Can you internal clients properly route to this subnet and resolve the pool name of your
edge pool? 
Ports and protocols poster, check out in A/V section client traffic to edge showing UDP/3478 and TCP/443:
http://www.microsoft.com/en-us/download/details.aspx?id=39968 
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SWC Unified Communications
This forum post is based upon my personal experience and does not necessarily reflect the opinion or view of Microsoft, its employees, or other MVPs.