How to use local private dns behind VPN connection.

What do I need to configure to allow use of local DNS
settings supplied by DHCP server on remote VPN connection.

Since installing the Microsoft Wireless-G base station, I
can not connect to private IP addresses when connected to
my workplace network using a VPN connection. If I ping
the mail server, the public IP address is returned but
while connected to the internal network via the VPN, I
need to use the private IP address.

IPconfig /all shows the correct DNS and WINS settings for
the remote network, but I appear to be using the DNS
settings from the LAN Base Station.