Changing Ethernet Addressing
1. Open System Preferences from the Dock or the Apple menu and then click the Network icon.
The Network window appears. On the left, you see a list of network ports, including AirPort.
2. Click the Ethernet port you want to configure.
3. Click the Configure pop-up menu and choose DHCP, Manual, or another type of addressing you’ll use.
4. In the appropriate fields, type the IP addressing and domain name information.
5. Click Apply.
After you change an IP address, you may have to update other settings, such as DNS.