IP address range

[David W. Hankins]

On Mon, Jul 27, 2009 at 09:22:28PM +0100, Simon Hobson wrote:
> That will not fix it - the DHCP server will still NOT give an IP address to 
> the client. The server MUST be able to associate the relay agent address 
> with a subnet, which means that the relay agent address MUST be within a 
> subnet that either hosts the client or is in a shared network with the 
> client.

This is correct but I want to be complete;

In 3.1.0 (and as 3.0.x is end-of-life this means "all current
releases"), we picked up support for the relay agent information
option link selection sub-option.

This means the relay agent can specify in 'giaddr' the address for the
server to direct replies to the relay agent, and specify in the link
selection sub-option the address to use to perform the "client
attachment" algorithm.

So a relay agent need not have an address on the subnet, or even that
link.  It just needs to supply an address within that subnet in the
link selection option (it doesn't need to own the address it supplies,
it is just informational).

So it is not precisely a MUST that the relay agent have an address on
the subnet.

-- 
David W. Hankins	"If you don't do it right the first time,
Software Engineer		     you'll just have to do it again."
Internet Systems Consortium, Inc.		-- Jack T. Hankins