Subject: RE: Relayed lease extension

From: "Barr Hibbs" <[email-masked]>
Date: Mon, 1 May 2000 08:33:36 -0700

This set-up might be used in other instances where the end-client never
gets an address via DHCP itself (if I recall, PPP sends it in the inital
negotiation to the client and thus the client isn't running DHCP at
all). If the BigBox gets the lease on the address for a shorter time
than the client is connected, it will need to renew the lease and hence
the situation Wim is looking at.

...Bernie, did you really mean to say that?  It seems to me that in the case
you describe, BigBox (and NOT its downstream client) is the host known to a
DHCP server as the DHCP client.  If you are suggesting a different
interpretation, such as BigBox acting as proxy for its client, then the
protocol may not adequately cover all implementation cases.

I do think this is a reasonable problem to solve and should be included
on the list of issues for revisions to the DHCP RFC. The simply policy
of sending the reply to the giaddr might be best and it is consistent
with what's done on the initial lease.

...I agree that we should consider this case.

Note: In the above case, I'm not sure I'd call the "DHCP thing" on the
"BigBox" a DHCP Relay. It really is more of a DHCP Client on behalf of
the actual client. If it is a classic relay, then as Bernard says, the
client is doing DHCP and thus there is no need for the relay to become
involved in the renewals.

...sounds suspiciously like a proxy to me when expressed in these terms....

--Barr

---

From: Bernie Volz <[email-masked]>
Date: Mon, 1 May 2000 15:31:31 -0400

>Even using the giaddr field does not solve all implementation
>scenarios.  The scenario I've been wrestling with is having a DHCP
>client (similar to the BixBox described previously) hosted on the same
>machine as a DHCP server.  In this scenario the client cannot use the
>giaddr field (to act as a DHCP relay agent) because the DHCP server port
>is already bound to the local DHCP server.
>
>Any ideas on how this can be accomplished using the current DHCP
>standards?  Does it make sense to support this scenario at all?

I guess that is a good point if you want to act as a relay on the same
system on which the server is running.

This would, however, also cause problems with the INITIAL lease
assignment and thus is not just with the renewal process.

Depending on your TCP/IP stack on the "bigbox", you may be able to
set up an alternate address and listen for packets on to that address
on port 68.

- Bernie