I am using Cisco Unified Communications Manager simultaneously through the CUCM Console (Web Server) and a Cisco 3825 Internal Router. Out of nowhere 2 days ago, every phone we have deployed off of the call manager randomly disconnects. Some will stay at "Registering" for hours, some will stay at "Restarting". Like I said, this happened out of nowhere. No configuration changes were made to my switch with the exception of a helper address. Coincidentally, we're having internet issues with clients on my client vlan. Has anyone ever experienced this issue? I'm running an old version of CUCM (220.127.116.11008-2) here at my deployed location because I believe that has been the only version that has worked for the rotations prior to me.
Based on your description, it sounds like you are having network problems. It is hard to say what without more information, but when more than one network service starts acting up at the same time, my guess would be a network issue.
If you added a helper address, that implies that something is doing DHCP that wasn't before. If the UCM was configured as the DHCP server, and now something else is, or is in addition (and on the same network segment) then ... well, that's not good.
If the phones change their address, subnet, etc they should restart.
I would revert the change you've made, then go from there. If the UCM isn't supposed to be serving DHCP any longer and is, disable the DHCP monitor service.