DHCP/BOOT protocols operate within a single physical subnetwork (client doesn't know his own and DHCP server addresses, so it's enforced to broadcast a message in a hardware layer). If a network is large, configuring and administrating separate DHCP/BOOTP servers (one for each subnetwork) becomes burdensome and error-causing.
DHCP/BOOTP Relay Agent allows to overcome these inconveniences. Within a subnetwork it is connected to (both at the Ethernet and at the WAN side), it looks for DHCP and BOOTP inquiries. Then it transfers the inquiries to a single or multiple central DHCP servers located at any place in the network. When a DHCP server transmits a response, the Relay Agent transfers it to the computer, which generated the inquiry.
As a result, even a very large network based on dynamic allocation of IP addresses and other parameters can be easily managed using a single server. Built-in server within Tahoe routers can be used for this purpose, or any other server compatible with RFC-2131.
