Apple has released
ChangeIPAddress v.1.0 script, which lets you change the IP address of a computer using Mac OS X Server 10.2 to 10.2.6. It’s a 50k downloadable file.
If the “Permanent IP Address” option was selected during the Open Directory Setup portion of the Setup Assistant, the primary IP address isn’t meant to be changed. However, you may need to change the IP address of the server at a later date.
The ChangeIPAddress v.1.0 script is designed to help you accomplish this. Or it can be used to assist you in recovering if you experience issues after having changed the primary IP Address of a Mac OS X Server.