XP clients sometimes ignore DHCPOFFERs

John Carr jbc4m at xmachina.itc.Virginia.EDU
Thu Mar 16 16:29:46 UTC 2006

We see this behavior quite often on our network.  Just yesterday we had
80 distinct MAC addresses ignore over 50 DHCPOFFERs each.  The top
"offer-deaf" client for the day ignored 1537 offers over a 2 and
one-half hour period.

I understand the initial failure when the windows client fails to ping
the gateway from the previous lease, but after it issues a DISCOVER, I
don't really know why it does not listen to the OFFERs.  The behavior is
clearly internal to the Microsoft DHCP client.  Yet it does not occur
every time you move a Microsoft client from one network to another.  I'd
love to see the state machine of the Microsoft client.  I suppose you
could gather enough data to figure out exactly what conditions trigger
this behavior and if anyone does, I'd like to know.  Until then we just
have the help desk tell people to go through a combination of
release/renew, reboot until they eventually get a valid address.

 John Carr                            Network Systems
 jcarr at virginia.edu                   ITC
 434-982-4710                         University of Virginia

 Hostmaster - DNS, DHCP & IP Address space management

On Wed, 2006-03-15 at 16:34, King, Michael wrote:
> > -----Original Message-----
> > From: dhcp-users-bounce at isc.org 
> > > On Behalf Of Sebastian Hagedorn
> > We have sniffed the entire "conversation" between client and 
> > server using Ethereal on *both* the client and the server. To 
> > my eyes everything looks the way it should look. We would 
> > like to just blame Microsoft, but I can't find anything 
> > regarding this in the KnowledgeBase and, more importantly, 
> > something must be different if this never happens with those 
> > routers at home.
> Actually, I think it's the home routers that are killing you.  :-)
> There is another Microsoft "Feature" you failed to mention:
> http://www.microsoft.com/technet/prodtechnol/windows2000serv/deploy/confeat/dhcpnt5.mspx
> If the DHCP client has previously obtained a lease from the DHCP server, the client tries to renew any unexpired lease with the DHCP server. If the client fails to locate any DHCP server, it attempts to ping the default gateway listed in the lease. If this succeeds, the client assumes it has not been moved and uses that lease. The client then seeks to automatically renew the lease when half of the lease time has expired.
> If the attempt to ping the default gateway fails, the client assumes that it has been moved to a network that has no DHCP services currently available, such as a home network and it configures itself. It then automatically keeps trying to find a DHCP server every five minutes.
> So.....
> Can these clients / you ping (or  If you can, that's why they won't let go of they're IP and take a new one.
> I had this problem for quite awhile. (Captive portal, answering to any address that would ping, and it was using as it's "DHCP" Server address.  We moved it to, and the problem went away)

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