10.2.3 Network Booting using BOOTP and TFTP

There has been much discussion of how routers can and should be booted from the network. These discussions have revolved around BOOTP and TFTP. Currently, there are routers that boot with TFTP from the network. There is no reason that BOOTP could not be used for locating the server that the boot image should be loaded from.

BOOTP is a protocol used to boot end systems, and requires some stretching to accommodate its use with routers. If a router is using BOOTP to locate the current boot host, it should send a BOOTP Request with its hardware address for its first interface, or, if it has been previously configured otherwise, with either another interface's hardware address, or another number to put in the hardware address field of the BOOTP packet. This is to allow routers without hardware addresses (like synchronous line only routers) to use BOOTP for bootload discovery. TFTP can then be used to retrieve the image found in the BOOTP Reply. If there are no configured interfaces or numbers to use, a router MAY cycle through the interface hardware addresses it has until a match is found by the BOOTP server.

A router SHOULD IMPLEMENT the ability to store parameters learned through BOOTP into local non-volatile storage. A router MAY implement the ability to store a system image loaded over the network into local stable storage.

A router MAY have a facility to allow a remote user to request that the router get a new boot image. Differentiation should be made between getting the new boot image from one of three locations: the one included in the request, from the last boot image server, and using BOOTP to locate a server.