Mac OS 7.5.3 and later support DHCP.

1. Goto the 'Apple' menu and select 'Control Panel'
2. Choose TCP/IP. The TCP/IP dialog will open.
3. Select the File menu
4. Choose 'Configurations' (a configuration dialog will appear).
5. Click 'Duplicate'
6. Rename the duplicate (e.g. 'AFN').
7. Select the name of the new configuration ('AFN') and select 'Make active'.
8. Select User Mode from the edit menu (the user mode dialog will appear).
9. Select the 'Active' option and uncheck the 'Load only when needed' option.
10. Select 'connect via -> Ethernet' in the TCP/IP dialog box.
11. Now, you will be able to select 'DHCP' as address assignment method.
12. Select 'Using DHCP Server' form the Configure menu. 
13. Close the TCP/IP dialog.
14. Save.