IP address change failed

We have changed IP addresses on a few SBS servers over the years and never had any real dramas using the Change IP address wizard from the server manager. That was until recently.
When we went to change the IP address we received an errors that IP change had failed. We set it back to the original and then tried to change it again. It took a few attempts but finally it did change.
We rebooted thinking everything would be fine but soon found errors with the DHCP server. It was working but we couldn’t view the DHCP server in the console manager. Also when we tried to do NSLOOKUP from the DNS console we got nothing.
The workstations all got their IP addresses correctly and everything seemed ok but we still felt that something was wrong. That night the backup software (Brightstor) failed backing up the Active Directory with Error E3156 EC8007003a. Also, the overnight SBS report was full of Exchange errors. There was definately something still wrong.
After extensive investigation as to why the server was still listing the old IP address in places, even after we successfully completed the change IP address wizard, it turns out that there was a manual entry for the server in the HOSTS file! Someone had manually gone into c:\windows\system32\drivers\etc\hosts and inserted an entry for the servername and the original (old) IP address. Clearly this will cause a problem since the HOSTS file normally takes precedence when doing IP lookups. Not wanting to point the finger at any party but it would appear that the previous IT people had made this entry because they had issues configuring something and thought it would fix their problems. Sure hope it did for them because it caused us no end of grief.
Once we removed the old IP entry from the HOSTS file everything started to magically work again (as it should!).
Moral of the story? Never, ever set a static IP address in the hosts file.

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