Dynamic Assignment

On local networks it is often the case that the user population changes frequently. New users arrive with laptops and need a connection. Others have new workstations or other network devices, such as smart phones, that need to be connected. Rather than have the network administrator assign IP addresses for each workstation, it is easier to have IP addresses assigned automatically. This is done using a protocol known as Dynamic Host Configuration Protocol (DHCP), as shown in Figure 1.

DHCP enables the automatic assignment of addressing information such as IP address, subnet mask, default gateway, and other configuration information. The configuration of the DHCP server requires that a block of addresses, called an address pool, is used for assigning to the DHCP clients on a network. Addresses assigned to this pool should be planned so that they exclude any static addresses used by other devices.

DHCP is generally the preferred method of assigning IPv4 addresses to hosts on large networks because it reduces the burden on network support staff and virtually eliminates entry errors.

Another benefit of DHCP is that an address is not permanently assigned to a host but is only "leased" for a period of time. If the host is powered down or taken off the network, the address is returned to the pool for reuse. This feature is especially helpful for mobile users that come and go on a network.

If DCHP is enabled on a host device, the ipconfig command can be used to view the IP address information assigned by the DHCP server, as shown in Figure 2.