Vista keeps name server options from previous lease

Frank Sweetser fs at WPI.EDU
Sat Sep 15 13:19:52 UTC 2007

Kirsten Petersen wrote:
> I realise this is probably not a ISC-DHCP issue, but if anyone has seen
> this and can provide insight, I would appreciate it.
> Our residence halls have a range where they hand out leases to unknown
> clients.  They also hand out a name server option different from the
> campus ones.  This name server redirects all requests to a registration
> page.  Once registered, the clients get a new lease, with the usual name
> servers, and go along their merry way.
> We also have a wireless network in the residence halls.  What we are
> seeing with Vista clients is this: the client picks up a lease from the
> wireless network and gets the options for the main campus name servers.
> Then, the user plugs into a wired port in the residence hall and gets a
> new lease from the dhcp server on that network.  However, their name
> server option does not get updated.  Thus, they don't get redirected to
> the registration page, because they are talking to the wrong nameservers.
> So, what seems to be happening is that Vista is keeping the name server
> options from a previous lease.  I haven't been able to find anything in
> the archives pertaining to this issue with Vista.  Has anyone else come
> across it?  Is it a Vista bug?

This sounds like you're running into an issue that's been brought up a couple
of times, so far with no resolution.  If you search through the list archives
for a thread with a subject of "dhcpinform request from Vista gets wrong Name
servers" you'll see all the details, but the short version is that the dhcp
server uses a slightly different set of logic to calculate what options should
be returned to DHCPINFORM requests than DHCPDISCOVER ones.

I'd love to see a fix for this myself, but whenever I code in C I have a bad
habit of making any programs within 10' catch fire and segfault.

Frank Sweetser fs at  |  For every problem, there is a solution that
WPI Senior Network Engineer   |  is simple, elegant, and wrong. - HL Mencken
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