Problems with Mac OS X Clients

David W. Hankins David_Hankins at
Mon May 8 18:54:01 UTC 2006

On Sat, May 06, 2006 at 08:24:00PM +0100, Adrian Merwood wrote:
> I am running 2 different (alternating) DHCP 3.0.3 servers - 1 on 
> Mandrake 2006 and 1 on CentOS.  They both exhibit the same behaviour.  

Did you build from source or package?

It's hard to tell if you're using LPF or BSD sockets for transmission
to these clients.

An easy way to find out is to examine the startup blurbs ("Listening
on ...").

I ask because I know some distributions have, in the past, intentionally
built using BSD sockets so that the dhcpd binary does not bypass firewall

I'm actually not sure what an OSX client will do if you use BSD sockets
to transmit to them (and get broadcast ip-address or ethernet mac wrong).
I've never tried it.  Windows sure doesn't like it though.  It's the FAQ
place to start looking: is your DHCP server producing all-ones broadcasts
meaning both IP address ( and mac address.

> May  6 20:15:32 gateway dhcpd: DHCPDISCOVER from 00:16:cb:07:49:93 via eth1
> May  6 20:15:32 gateway dhcpd: DHCPOFFER on to 
> 00:16:cb:07:49:93 via eth1

Presuming the OFFER gets to the client (questionable but easy to
verify if you own the client), and presuming the REQUEST, if any, would
be able to reach the DHCP server (highly probable considering the
DISCOVER does), then the only remaining explanation is that the client
doesn't like something in (or not in) the offer for some reason.

This is an Apple question, not an ISC one...we can only speculate as to
what it finds lacking in the offer.

> The address is from another network served by a built in 
> DHCP server on an ADSL router which happily serves up addresses to OS X.

We have a few OSX boxes here at ISC, and have had no issues.  I suspect
the difference is that we don't utilize RFC1918 addresses.

So this is possibly OSX brain damage stemming from the belief that the
client has not changed networks (it's still on the same subnet).

See also:

Which I don't know if the OSX client implements or not, but it does
have an Apple employee on the authors list.

If all else fails, compare ethereal traces of the two networks from
the client's point of view.  See what's different.  Don't filter the
trace down to just DHCP - you want to see ARP and maybe ICMP too.

If you don't mind emailing them to dhcp-bugs at, I get a kick
out of looking at DHCP packets over lunch sometimes.

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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