HP 200 Series Services And Applications page 140

Internet Protocol Routing Service
BootP and DHCP
Figure 16. Bootrequest Relay with No Specific Server or Subnet
The Bootp relay agent can be configured with a list of destination addresses
for Bootrequest packets. An address on this list can be any one of three
types, as follows. The relay agent generates one or more Bootrequest
packets for each address on the list, depending on the address type.
Specific Host Address is the address of a Bootp server somewhere
on the network. The relay agent sends the Bootrequest packet to the
specific host address. In this case, the Bootrequest is routed through the
network to the Bootp server just like any other IP packet. No other relay
agents are needed other than the router adjacent to the client.
Subnet Address is an IP address with a valid value for the network
number and subnet number, but either all zeroes or all ones for the host
part. For example,, the class A network number 15 with a subnet mask
of 255.255.255.0 has the valid subnet address 15.1.1.0; 15.1.1.255.
The address 15.1.255.255 would not be a valid subnet address. This would be
treated as a broadcast to all subnets in network 15. If a subnet address is
configured as a Bootrequest destination,, the relay agent will set the destina-
tion IP address of the Bootrequest to the subnet address. The IP layer in the
router will send the packet out whichever interface provides the shortest
path to that subnet. The Bootrequest will be routed through the network to
the subnet just like any other IP packet. No other relay agents are needed
other than the router who is adjacent to the client.
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