External DNS Errors on SBS 2008 Network

We came across a problem where, intermittently, when trying to access websites on top level domains like .com or .co.uk, we would get a "Server cannot be found error".

Our ISP confirmed that they had no issues their end, so we looked towards our network for a reason for the problem.

Our DNS is controlled by a server running Windows Small Business Server 2008. The issue lies here.

If you are having similar issues, try doing the following to your DNS server:

Note: Steps are detailed for use with Windows 7 and Windows Small Business Server 2008 but you may still find this tutorial useful if using other software.

Before we start, you will need to have your ISP's DNS server IP address. You can get this either by a Google search or contacting your ISP directly.

• Click Start
• In the search box, type "DNS" and click "DNS" under Programs
• If a "User Account Control" (UAC) message pops up, click continue
• On the left hand side of the window that will show, right click your server's computer name and click properties

• Click on the "Forwarders" tab

• Click Edit
• Type the IP address of your ISP's DNS server and press "Enter"

• Click OK

Now do the following on each terminal machine, or set up the below settings using a group policy object on your domain server:

• Click Start
• In the search box, type "view network connections" and click the "view network connections" item listed under control panel
• Right click the  connection that links you to your office network (usually "Local Area Connection") and click "Properties"

• Select "Internet Protocol Version 4 (TCP/IPv4)" and click properties
• Click the "Use the following IP address" radio button and the "Use the following DNS server addresses" radio button
• Type an IP address for your machine. It is usually a good idea to use the IP address it is currently using.

(Find out your current IP address by holding down the windows key and pressing R, then type "cmd" and hit enter. Then type "ipconfig" and hit enter. Find the details for your network connection (the same one you right clicked on earlier) and you will see your local IPv4 address listed underneath it.)

• Type the subnet mask for your machine. Again, use the same one as you are currently using. Follow the same steps noted above to find your current subnet mask. It is usually, "255.255.255.0"
• Type an IP address for your default gateway. Again, best to use the one you are already using. Follow the above steps to find it out. It is usually the IP address of your router.
• In "Preferred DNS server" type the ip address of your DNS server
• In the "Alternate DNS server" type the ip address of your ISP's DNS server.
• Click OK.
• Click Close.
• Exit the network connections window.

And you are done. You should now check connectivity to your other network computers and external websites.