Using DNS Conditional Forwarders (Windows)

Occasionally you run into the website or two that will not resolve properly using your own DNS servers.  Some people simply set up global forwarders for their DNS server.  I don’t recommend doing this because it can cause problems resolving addresses on your local network, especially if you have multiple sub-nets or even multiple routed networks.

The better solution is to use conditional forwarders.  Conditional forwarders allow you to specify a DNS server to use for a particular domain.  In my case we had problems resolving paypal.com from one of our networks.  By setting up a conditional forwarder, we were able to address the paypal problem without causing DNS resolution problems for other domains or our own networks.

Here is how its done on a Windows 2008 DNS Server (all Windows Servers are typical):

1. Open the DNS manage from Administrative Tools int the control panel.
2. Navigate to and right click on Conditional Forwarders under your DNS Server. then select “New Conditional Forwarder”
3. Enter the Domain of the site you want to resolve using forwarders
4. Enter the DNS Server to use for resolving this domain.  I used one of Level3's and one of Google’s in this case.  OpenDNS Servers are also a good choice.
5. If you use Active Directory, make sure you check the box to store in Active Directory.  That way the forwarder will replicate to your other DNS Servers.  The default’s are ok for the rest of the settings.

You may need to clear your DNS cache to get this working.  You can do this by right clicking on the DNS Server in DNS Manager and then selecting "clear cache".   You and calso do this from the command prompt by typing
"Dnscmd ServerName /clearcache".  While your at is run "ipconfig /flushdns" to clear the DNS cache on your local computer.

Enjoy!

(Note: This was originally published on my blog, and has been expanded for the Experts Exchange article.)