Part of our decommissioning of our Lync 2013 environment is pointing our hardware load balancer so that calls to URL's get directed to our SFB FE server instead of our Lync 2013 FE servers. When we added a SFB FE server which is running Windows 2012 R2, we start getting 403 errors. "The credentials you supplied do not have permissions........" We were not experiencing this issue with Lync 2013 which runs on Windows 2008 R2. I am guessing now that there is tighter security in 2012 R2 IIS. We noticed that if we enable Directory Browsing on the External and Internal Sites on the SFB FE server, the error goes away, but probably not a good solution. Hoping someone else ran into this issue and can help out.
Error we get when trying to browse to the server using IE. Doesn't happen with Lync 2013.