Lync 2013 migration – Cannot sign-in when IPv6 enabled

After nearly a day trying to figure out why a newly deployed Lync 2013 pool would not allow users to sign in, and just before I was about to pull my hair out, I found IPv6 was to blame. Normally I would always disable IPv6 during server preparation, however in this case the job was already done for me and I didn’t check. Now the weird thing here, is that Lync 2013 supports IPv6!

Here is the original description of the problem I posted on TechNet:

“I have 3 domains in 3 country’s. US and Australia has a working Lync 2010 deployment, and we have just added a new site in the New Zealand domain with Lync 2013 (eventually the other sites will be migrated to Lync 2013). The Lync 2013 Front End has been installed and all services are running. I have enabled the first test user in the Lync Control Panel successfully . When I go to sign-in I get an error along the lines of “try again or check with your administrator”. On inspection of the client logs I can see that client sends a SIP register, the server responds with the available authentication methods, the client then trys again with using Kerboros and the server responds with SIP/2.0 404 Not Found – ms-diagnostics: 4005;reason=”Destination URI either not enabled for SIP or does not exist”. The use account is valid and I can log on to a workstation successfully with the same account.

We have not yet run enable-cstopology on the Lync 2010 FE’s as this is not normally required. However to be safe this is currently going through change control. Something that isnt common in a migration is adding a new SIP domain (for New Zealand) and new meet and dialin URL’s. This makes me think that running enable-cstopology on the Lync 2010 FE’s will fix it. The other thing that springs to mind is domain secuity on containers and OU’s etc”

Just in case IPv6 was a red hearing I better let you know that about an hour before I changed the user replication cofiguration. Get-CSUserReplicatorConfiguration identified that only the domains where Lync 2010 existed where part of the user replication cycle. To fix this issue I added the domain, ran a sync and rebooted for good measure.

This did not produce any immediate results, however you never know, time can be a healer.