How does DHCP and BOOTP handle multiple subnets?
For the situations where there is more than one LAN, each with its own subnet number, there are two ways. First of all, you can set up a seperate server on each subnet. Secondly, a feature of some routers known as “BOOTP forwarding” to forward DHCP or BOOTP requests to a server on another subnet and to forward the replies back to the client. The part of such a router (or server acting as a router) that does this is called a “BOOTP forwarding agent”. Typically you have to enable it on the interface to the subnet to be served and have to configure it with the IP address of the DHCP or BOOTP server. On a Cisco router, the address is known as the “UDP Helper Address”. • Can a BOOTP client boot from a DHCP server? Only if the DHCP server is specifically written to also handle BOOTP queries. • Can a DHCP client boot from a BOOTP server? Only if the DHCP client were specifically written to make use of the answer from a BOOTP server. It would presumably treat a BOOTP reply as an unending lease
