Configuring TCP/IP en masse using DHCP

If you're the network administrator of a large network, you don't want to run around to 400 workstations and configure an IP address, subnet mask, and default gateway on each computer. Not only is this time-consuming to initially set up, but it also becomes a nightmare to manage because of all the potential for human error. I have spent my days running around to each computer on the network, a sheet of paper in my hands, making sure that each computer is configured properly.

Today's network operating systems support a feature called Dynamic Host Configuration Protocol (DHCP). DHCP is a standard that allows the network administrator to tell the DHCP server a range of IP addresses that it is allowed to give out, along with the other TCP/IP options such as a subnet mask and default gateway. When the DHCP server has been configured to give out the addresses, the desktop computers automatically request an IP address from the server when they start up, and the server hands them all the IP address information. This means that the network administrator doesn't have to run around to each computer individually to configure TCP/IP, and in the long run, that saves time and money.

The steps to configure a Windows 2000 or XP system to obtain an IP address from a DHCP server are very similar to actually assigning the IP address manually.

To configure a Windows 2000 or XP client for DHCP, follow these steps:

1. If you're using Windows 2000, choose Start → Settings → Control Panel → Network and Dial Up Connections. If you're using Windows XP, choose Start → Control Panel → Network and Internet Connections → Network Connections.
2. Right-click your local area connection and choose Properties.
3. In the list of items used by the connection, select TCP/IP and click Properties.
   The Internet Protocol (TCP/IP) Properties dialog box appears.
4. On the General tab, select the Obtain an IP Address Automatically option, to enable this system to be a DHCP client.
5. Click OK and then OK again to close the network connections dialog box.

Automatic Private IP Addressing

If a DHCP server isn't available, and your Windows clients are configured to obtain an IP address automatically, will they receive an IP address? For operating systems before Windows 98, the answer would be no. But all versions of Windows since Windows 98 support a feature called Automatic Private IP Addressing (APIPA). APIPA is a feature that allows the client to self-assign an IP address if the DHCP server doesn't respond to the DHCP request. The address that the client self-assigns is within the 169.254.x.y network range. The system will also configure itself with a subnet mask of 255.255.0.0 but will not configure the default gateway entry. This means that if the DHCP server is down and your network clients boot up, they will all have an address in the 169.254.x.y range and will be able to communicate with one another. Because they are not configured for a default gateway entry, they will not be able to communicate with systems off the network or with the Internet.