In large routed network environments, routers are used to direct IP packets between different subnets. As such, routers are perfect candidates to be DHCP relay agents.
In this section, I will explain how to configure a Cisco router to act as a DHCP relay agent. Although there are other manufacturers of routing equipment, I am describing this configuration because Cisco is the de facto standard in routers. To configure other routers, please refer to the product documentation.
There are many aspects to correctly configuring a Cisco router. This book describes the configuration of the DHCP relay agent. Please see other O’Reilly books for more information on configuring Cisco routers.
The following configuration is based on a Cisco Systems 2500 router using the Cisco IOS Release 12.0:
Using either Telnet or terminal emulation, establish a connection with the router.
If prompted for a password, enter it now.
At this point, the router is in user mode. User mode can be used to get basic information about the router.
Next, enter privileged mode by entering the following command at the console prompt:
If prompted for the enable password, enter it now. The prompt now looks like the following:
To enter configuration mode, the
terminal command must be used. The
executes commands entered at the router prompt. Enter
terminal at the
config terminalEnter configuration commands, one per line. End ...