Relay agents, NAT, and offers to giaddr

Alan DeKok adekok at
Fri Sep 15 15:10:27 UTC 2006

Simon Hobson wrote:

> Not true. It is true that relay agents are usually run on routers but 
> it is NOT required - all that is required is that there is a relay 
> agent somewhere on the client network.

   The router usually has a better idea about network topology than 
other devices, which is a good reason for making it the relay agent.

> No, it still will NOT work. The GIAddr will still be a non-routable 
> rfc1918 address.

   That's really an implementation choice.  NAT boxes already keep state 
for UDP queries and responses, and re-write packet contents.  There's no 
reason the NAT box can't do NAT for DHCP relay, too.  In that case, 
giaddr could be its external IP.

   i.e. NAT boxes already re-write packet contents for things like icmp 
port unreachables, why not do the same for DHCP?

   Alan DeKok.

More information about the dhcp-users mailing list