Warning: subnet overlaps subnet

David W. Hankins David_Hankins at isc.org
Tue Mar 18 20:53:06 UTC 2008

On Tue, Mar 18, 2008 at 11:38:05AM -0500, John Hascall wrote:
> OK.  Let me step back.  Here's what I would like to accomplish.
> We have two DHCP servers.  We do not use failover.
> One is the main DHCP server.  It handles everything.
> The second is maintained as a warm spare, but it does
> serve out addresses for all the fixed-address machines.
> All this works fine.  We have monitoring software that
> basically sends DHCPINFORMS at the dhcp server and
> waits for the acks.  This works good for the primary,
> but the second server never answers because it is
> not authoritative.  My one host subnet was an attempt
> to make the second server answer the monitoring host.

let me quote you the comment on the code that decided to overload
the 'authoritative;' flag with whether or not to respond to

        /* We don't respond to DHCPINFORM packets if we're not authoritative.
           It would be nice if a per-host value could override this, but
           there's overhead involved in checking this, so let's see how people
           react first. */

it's been a few years since that comment was written, but it appears
that you are "reacting" negatively to this author's comments.

i think the answer hopefully does not involve gymnastics in the subnet
sources to permit overlapping regions.  we should just create a config
option for this and default to inspecting authoritative in its absence.

Ash bugud-gul durbatuluk agh burzum-ishi krimpatul.
Why settle for the lesser evil?	 https://secure.isc.org/store/t-shirt/
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

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