DHCP for Automatic IP Address Assignment on Your MacBook - dummies

DHCP for Automatic IP Address Assignment on Your MacBook

By Mark L. Chambers

Dynamic Host Configuration Protocol, or DHCP for short, is a protocol that enables your MacBook to retrieve all the networking information you need. Before you can use DHCP, you have to add a DHCP server, which provides other computers on the network with their configuration settings.

Most Internet connection-sharing hardware devices (and software-sharing implementations as well) provide a DHCP server as part of the price of admission. (Internet connection sharing allows all your networked computers to access the Internet through a single Internet connection.) Most wired and wireless routers can provide DHCP services these days. Technology marches on.

If you plan to use Internet connection sharing or you know that you have a DHCP server on your network, you can set up your MacBook to automatically obtain the required IP address and information. Open System Preferences from the Dock or the Apple menu and choose Network.

From the Network dialog that appears, click the Ethernet entry in the list on the left. Choose Using DHCP from the Configure IPv4 pop-up menu; then click the Apply button. Mac OS X contacts the DHCP server to obtain an IP address, a subnet mask, a gateway router IP address, and a Domain Name System (DNS) address. (DNS servers convert a human-friendly address to a computer-friendly IP address, like

A few seconds after clicking the Apply button, you should see the information come up, as provided by the DHCP server. This lets you know that the process worked and configuration is complete. You might also notice that the DNS Servers information is empty (or grayed out).

Fear not: Mac OS X is really using DNS information provided by the DHCP server. Press Command+Q to quit System Preferences and save your settings.

If you ever make a network change that screws things up, such as entering the wrong subnet mask or an IP address that isn’t in the same range as others on your LAN, you can always click the Revert button to get back your old settings.

One DHCP server on a network is princely, but two or more DHCP servers on a single network will fight like alley cats and grind everything to a halt. Therefore, if you’re considering adding a DHCP server to an existing network, make doggone sure that you’re not treading on another server’s toes. (Ask that network administrator person.)