The Case for Server-Supplied IP Addresses

Every computer, as you learned in a previous hour, must have an IP address to operate on a TCP/IP network. The IP addressing system was originally designed for the logical condition in which each computer is preconfigured with an IP address. This condition is known as static IP addressing. Each computer knows its IP address from the moment it boots and is able to use the network immediately. Static IP addressing works well for small, permanent networks, but on larger networks that are subject to reconfiguration and change (such as new computers coming and going from the network), static IP addressing has some limitations.

The principal shortcomings of static IP addressing are

• More configuration— Each client must be configured individually. A change to the IP address space or to some other parameter (such as the DNS server address) means that each client must be reconfigured separately.

• More addresses— Each computer uses an IP address whether it is currently on the network or not.

• Reduced flexibility— A computer must be manually reconfigured if it is assigned to a different subnetwork.

As an answer to these limitations, an alternative IP addressing system has evolved in which IP addresses are assigned upon request using the DHCP protocol. DHCP was developed from an earlier protocol called BOOTP, which was used primarily to boot diskless computers. (A diskless computer receives a complete operating system over the network as it boots.) DHCP has become increasingly popular in recent years because of the dwindling supply of IP addresses and the growth of large, dynamic networks.

It is quite likely that the majority of all computers with Internet access receive their configurations through DHCP. The small router/firewall device that brings the Internet to your home network is probably also acting as a DHCP server.