LYNC - Use F5 LTM as reverse proxy?

I assume you are using the same cert and key on the external 443 VIP that you have configured in Lync for your web services, the Lync servers can connect to the Certification Authority and validate the cert, and that this external VIP is using a serverssl profile as well.

 

 

Have you tried running the Lync logging tool on the FE servers? This is usually pretty helpful, and would tell you right off the bat if the connection is even making it to the FE.

 

 

I recommend opening a support case. This will help track issues with the solution and allow us to have a look at your config.