DHCP in Routed Networks

In routed networks that use subnets to divide network segments, administrators must observe some specific requirements for a full implementation of DHCP services to function. These requirements include one of the following:

• One DHCP server must be located on at least one subnet in the routed network.

• For a DHCP server to support clients on other remote subnets separated by routers, a router or remote computer must be used as a DHCP/BOOTP relay agent to support forwarding of DHCP traffic between subnets.

Figure 4.17 illustrates an example of a routed network with a DHCP server and DHCP clients.

Figure 4.17 An Internetwork Using Automatic TCP/IP Configuration with DHCP

As explained earlier, routers that implement the DHCP/BOOTP relay agent can be used to route traffic between DHCP servers and clients located on different subnets. The relay agent on the router forwards requests from local DHCP clients to the remote DHCP server and subsequently relays the DHCP server responses back to the DHCP clients.