In this article: http://docs.info.apple.com/article.html?path=ServerAdmin/10.5/en/c7sa13.html Apple states that you no longer need to use the changeip command with Mac OS X Server:
You can change the IP address of a server using the Network pane of System Preferences or the networksetup tool.
When a network address change is detected, no matter how the change happened, changeip is invoked. The tool changeip goes through all configuration files and places where the Server’s IP address is stored, and changes the address to conform to the new address. The server’s IP address can be changed without changeip being invoked from the command-line.
