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Re: problems with having two DHCP servers...

On 01/05/12 16:30, John A. Sullivan III wrote:
On Thu, 2012-01-05 at 15:55 -0500, Rick Thomas wrote:
On Jan 5, 2012, at 1:40 PM, John A. Sullivan III wrote:

On Thu, 2012-01-05 at 12:57 -0500, Rick Thomas wrote:
A limited amount of redundancy is good.  If one goes down, the
can still limp along.

Anyway, that's the theory.


On Jan 5, 2012, at 10:07 AM, Osamu Aoki wrote:

I'm not the OP, but I do have this problem.  When I try to do an
install (wheezy) on a network with two DHCP servers, the
dhcp-client never seems to get an IP address -- even though the two
servers are both responding and both giving the same IP address.
Then why have 2?

The problem is when they are administering addresses in the same
I've not configured DHCP for a long time so maybe this is common now
the problems have all been resolved but, in the past, if one wanted
redundancy, one would administer different ranges on the same subnet
that there would be no conflicts.  Hope that helps - John
Yes, that does seem to fit.

The two servers have different ranges for their "dynamic" clients
(i.e. transient laptops with no fixed IP address) but for the "static"
clients (desktops with a fixed IP address) there is only one address,
so both servers have to provide the same address.

So... when I do an install for a machine with an unknown Ethernet Mac
address -- hence getting it's IP from one or another of the "dynamic"
ranges -- all goes well.  It's only when I attempt to install a
machine with a known Mac address (hence a single static IP) that I run
into trouble.

Somehow, I would have thought it should be the other way round --
conflicting responses would cause problems, not two responses that
both say the same thing.  Sigh!  Just shows how much I know...

So is there a way to have both redundancy *and* reliable installs?

Thanks for any help,


PS: As others have noted, it seems to affect only the installer's DHCP
client.  After the reboot, there's no problem -- with either static or
dynamic IP...

Hmm . . . could you install with a manual IP address and then simply
change the configuration once the installation is done? - John

Of course. And that's exactly what I usually wind up doing. Though now that I've discovered that temporarily killing one of the dhcp servers works, I may do more of that in the future.

Really, I'm mostly interested in figuring out what's going on and probing to help get it fixed.



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