XP VPN - Force nslookup to use DNS servers supplied by RRAS?

[Eric McWhorter]

Hello -

I've got a peculiar problem. Quick overview of the setup: Windows XP Pro
client connecting to office LAN via Windows VPN connection (PPTP), with "use
default gateway on remote network" unchecked. Typically, in this
configuration, the client will attempt to connect to a server on the LAN by
name, and a DNS lookup will occur - first to the client's primary internet
connection's defined DNS servers, and since that usually fails (due to the
FQDN being of an unregistered domain like machine.domain.local or something
like that), a DNS lookup is attempted using the DNS servers supplied by the
RRAS server, which provides the correct LAN IP address for the server, and
connectivity can be established.

Well...a few of my users, who frequently use the Windows VPN connection to
connect to the office to connect to the Exchange server, gain access to
network shares, etc., began having an issue whereby their ISP's DNS servers
had begun returning a PUBLIC IP for any host they were attempting to look
up - even those with fake names. Basically, you could type nslookup
blah.bogusfqdn.com (which I have checked, and doesn't exist) and it would
happily return a public IP (I don't know which IP it acutally is, possibly
their ISP DHCP assigned IP). While the client is still able to gain basic
TCP/IP connectivity to the LAN, in essence, they've lost the ability to look
up any host on the LAN.

It seems to be an SBC DSL problem specifically, as users who have, for
example, Comcast bandwidth do not experience the same behavior.

I know that we can counteract this by re-checking the "use default gateway
on remote network" setting, but our office bandwidth isn't the greatest, so
we don't get the best results with that. Is there any other way to
automatically force the client to look up hosts that match a certain domain
name (i.e. our AD domain) to use the DNS hosts specified by the RRAS server?

Thanks!

- Eric McWhorter

 

[pariah]

Hi,
I had exactly the same problem, and this resolved it:
You must change the Binding order of your network interfaces so that
the RRAS connection is top of the list. Then when you are connected to
the VPN, the settings (DNS etc) of this connection takes priority.
This is normally done in the Advanced Settings box (Network
Connections, Advanced, Advanced Settings, Adapters & Bindings). However
in windows 2k & Xp, this settings does not work, and the regisrty must
be edited. Please refer to the Microsoft paper on this for
instructions:
http://tinyurl.com/bzjxx

Also, you must have the Use Default Gateway On Remote Network ticked to
prevent dual-tunneling, which is a security risk.