Relay agents, NAT, and offers to giaddr

Simon Hobson dhcp1 at
Fri Sep 15 21:58:53 UTC 2006

Alan DeKok wrote:

>  > It doesn't deal with the client renewing though. That would need
>>  significant rewriting of the server to handle renewal requests that
>>  come from a different IP address to the lease being renewed. IFF you
>>  think you can write a workable method for dealing with it, then the
>>  way to address it is through the standards bodies - good luck !
>    Maybe I'm crazy, but my tests with ISC & a hacked-up test client
>indicate that so long as giaddr is set, that's where the reply goes.
>I've successfully had it renew leases for IP address X that were unicast
>from IP Y (i.e. giaddr).

Clients renewing do not use a relay agent - they unicast directly to 
the server.

So now you have to capture and mangle unicast packets as well as 
broadcast - yet another special case ALG.

More information about the dhcp-users mailing list