Youcan configure more than one boot file in the boot configuration database by
specifying the path and name of each boot file (using the add command described
on page “Add” on page94). If you have more than one host server, you can use a
different host server to boot the router when another host server cannot be reached
over the network.
Toconfigure booting:
1. Add an address record, using the add address command from the Boot
config> prompt, that specifies the interface from which you want it to boot.
2. Add the boot record, using the add boot-entry command from the Boot
config> prompt, specifying the host address, next hop router (if necessary), and
the path and filename of the host.
Using a Device as a Boot Server
A device can also function as a boot server.Devices that do not have an IBD can
obtain their load files or boot files from a router that has an IBD. Use the add
boot-entry command to designate the location of the router with the boot file. Make
sure that you include the entire path name of the load file with this command. On a
router with the load in IBD, this is IBD/filename.
How the BOOTP Forwarding Process Works
BOOTP (documented in RFC 951) is a bootstrap protocol used by a router or a
diskless workstation to learn its IP address, the location of its boot file, and the boot
server name. Adevice can act as a

BOOTP client

or as a

BOOTP relay agent

for
another device. The following sections describe these two processes.
A Device as a BOOTP Client
A device acts as a BOOTP Client when it needs to find the location of the boot file
and boot server. Youcan specifically configure the device’s boot PROM
configuration record so the router can act as a BOOTP Client, or it can become a
BOOTP Client if, during booting, it does not contain a valid file name and path to
the location of the boot file and server. When either of these two conditions exists,
the router broadcasts a UDP packet over one of its LAN interfaces to the

BOOTP

server

that contains the path name of the boot file and server.
The following describes the BOOT client forwarding process:
1. The BOOTP client copies its MAC address (either Ethernet or TokenRing) into
a BOOTP packet (UDP packet) and broadcasts it onto the local LAN. BOOTP is
running on top of UDP.
2. The BOOTP server receives the request and looks up the client’s Ethernet
address in its database. If found, it formats a BOOTP reply containing the
client’s IP address, the location of its boot file, and the boot server name. The
reply is then sent back over the LAN to the BOOTP client.
Note: If multiple hops are required before reaching the BOOTP server, a
BOOTP relay agent receives the packet. BOOTP relay agent is explained
in the next section.
3. When the router receives the BOOTP reply packet, it uses the information it
contains to initiate a TFTP request to the boot server.
Using the Boot CONFIG Process
84 MRS V3.2 Software User’s Guide