DNS Resolution for Lync 2010 Edge Server

The other day, I encountered a Lync 2010 AV Edge-related issue. I'm getting a "Call failed due to network issues" in my Lync client, both from the remote user, and the internal user. The call automatically drops if an external (remote) user is calling an internal user, and vice-versa. Based from past experiences, the initial testing I did in hope to troubleshoot the issue was about DNS resolution. Below are the procedures I ran through with the expected results. This is a good checklist when you are working on your Lync 2010 Edge server.

Procedure #1

Please do this on the Lync Edge Server

Task	Expected Behavior
Ping sip.contoso.com	Should resolve either the public IP, or the DMZ external IP of Access Edge Server
Ping wc.contoso.com	Should resolve either the public IP, or the DMZ external IP of Web Conferencing Edge Server
Ping av.contoso.com	Should resolve public IP of AV Edge Server
Ping lyncfe.contoso.domain	Should resolve private IP of Front End Server

Procedure #2

Please do this on any internal computer

Task	Expected Behavior
Ping av.contoso.com	Should resolve public IP of AV Edge Server
Ping lyncedge.contoso.domain	Should resolve internal IP of Edge Server

Procedure #3

Please do this on the Lync Front-End Server

Task	Expected Behavior
Ping av.contoso.com	Should resolve public IP of AV Edge Server
Ping lyncedge.contoso.domain	Should resolve internal IP of Edge Server

Procedure #4

Please do this on any external (remote) computer

Task	Expected Behavior
Ping sip.contoso.com	Should resolve public IP of Access Edge Server
Ping wc.contoso.com	Should resolve public IP of Web Conferencing Edge Server
Ping av.contoso.com	Should resolve public IP of AV Edge Server
Ping lyncedge.contoso.domain	Should resolve internal IP of Edge Server

It turned out; calls are dropped because one item above failed. How did I know? I enabled Windows Event logging in Lync and saw an error on the client side that points directly to an unresolvable host name. I can’t ping the internal host name of the Lync 2010 Edge Server (lyncedge.contoso.domain) from any internal computer. I double checked my internal DNS and I found out an A record for the internal host name of the Edge Server was not created. Thus, after creating the A record, and having internal computers resolved it, it solved the issue!

If you encounter a similar problem, I hope this helps!