1. From the Apple menu, select System Preferences
2. In the Internet & Network section, click the Network icon.
3. Select Built-in Ethernet
4. Click on the padlock to be able to make changes. You will be prompted to enter your administrator username and password.
5. Click Advanced (Mac OS X Leopard)
6. In the TCP/IP tab, ensure that Configure is set to Using DHCP
7. Ensure that DHCP Client ID, DNS servers, and Search Domans are empty.
8. Click Apply Now and press the Apple key and the Q key together to quit System Preferences