dhcpinform request from Vista gets wrong Name servers

David W. Hankins David_Hankins at isc.org
Wed Aug 15 18:16:51 UTC 2007

On Wed, Aug 15, 2007 at 12:05:16PM -0400, Randall C Grimshaw wrote:
> The Vista machines initially get the correct DNS settings and query for isatap (which resolves to the registration system) then queries for teredo.ipv6.microsoft.com (which resolves to the registration system).... then the rub... the Vista machine will perform a dhcpinfo query for name servers among other things and get the default name servers in the dhcpack - the default (production) name servers cannot be reached from the captive subnets and wouldn't direct users to the registration system if they were.
> I am not sure if this is a bug in ISC dhcp by RFC or not.

It's (very) cloudy.  The final answer is that ISC DHCP should provide
the nameservers you /want/ it to provide in DHCPINFORM.  We don't.

I would say we need to update ISC DHCP to address this, but I'm not
precisely sure how...an exclusion list of 'things not to send in
DHCPINFORM', sourcing the client's active binding in DHCPINFORM to
bring in all that you know about it...

> Does snyone know if the dhcpinfo is a response to unexpected answer to the other two queries?

It's hard to say...Windows boxes (XP and Vista alike) will DHCPINFORM
for many reasons, none of them can be reliably predicted (windows
updater, Flash Proxy Autodetection, etc).

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

More information about the dhcp-users mailing list