A. Windows 2000, Windows NT, and Windows 9x let you identify multiple DNS servers. So, for example, you might have a local DNS server on your network and a remote DNS server if you connect to the Internet. In this situation, if you list your local DNS server first, you might not be able to resolve remote names, and if you list the remote DNS server first, you might not be able to resolve local names.
In a multiple DNS server environment, if a client queries the first DNS server and that server doesn't respond, the client will query the second DNS server. If the first DNS server (e.g., a local DNS server that doesn't know about a remote host) responds with an unknown host, then the client won't query other DNS servers. Instead, the client will resort to using other methods (e.g., LMHOSTS, WINS) to resolve the domain name.
To work around this problem, you need to configure your machines to forward DNS information, which typically means configuring local DNS server information on the clients and configuring the local DNS servers to forward unknown requests to the remote DNS servers.