I've inherited a fairly large infrastructure. And I'm drawing a blank on determining how external DNS is given to clients on our internal network. All systems have a DNS ip address from DHCP and when I do an nslookup on say www.yahoo.com it resolves. But I can't figure out how this external resolution is taking place. I've had a client in the past who used a 3DNS device? Anyway to find this out? Thanks in advance!

Are the DNS servers handed out via DHCP Windows Based? If so, you can check them to see if they have forwarders (possibly to an ISP DNS server) or root hints configured. After logging in to the DNS, this is part of the DNS mmc snap in, (accessible from Start -> Control Panel -> Administrative Tools). Then click the server in the left pane, right click, and select properties. The two tabs in the properties view are called Forwarders and Root Hints. If they are BIND based (or use another DNS server software), post back to this thread and we can try to determine where to look on them. -- Mike Burr

You clients, which are using internal DNS server, ask the server for DNS resolution like www.yahoo.com. This server forward the request to an external DNS server which solves the request and return it to your internal DNS server. At this step, your internal DNS server will return the response to your client computer which requested the resolution. Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. Best regards.

This is a link for a video that will explain to you to configure a forwarder on a Microsoft Windows DNS server: http://www.laboratoire-microsoft.org/videos/10191/ Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. Best regards.