wer are running 12.? on the system. We had to upgrade our certificates to fix an issue with Extension Mobility, restarted the Tomcat service and Ext. Mob. works, but since the corporate directory has failed. I have tried restarting the TomCat service a couple of times but it still does not work.
From another Post
If you are getting Host not found error then please find below of the steps to remove this error:-
Make sure to change hostname to ip address under System->Server.
As a workaround, remove the Secure URL entry for Directory URL under the Enterprise Parameters.
Make sure that the firewall settings are not blocking access.
Restart the Cisco Trust Verification Service.
Also refer to the link below for more information
So, you will be able to see in the phone logs what is happening here.
host not found can indicate that trust is broken. That should not happen if you follow the proc and only touched tomcat certs, unless it was broken before.
If that’s the case then you’re in for a bulk ITL erase since the phones no longer trust the UCM.
There IS ITLRecovery, and hopefully on 12 the dumb bugs that break that with FIPS or just in general are resolved.