If you're using Active Directory, you're probably also using Microsoft's DNS bundled with Windows Server 2003. By default, Windows Server 2003's DNS uses a mechanism known as "round robin" to achieve load balancing. While, on the surface, this is a good thing, there may come a time when you do not want to allow this load balancing to occur. Fortunately, it's not too hard to disable.
First, let me explain a little about round robin DNS resolution. Imagine you have three Web servers, all replicated with one another and all serving identical content. In your DNS, you have three entries with the same name, but each entry has a different IP address—one address for each Web server. Now, suppose you have three clients all loading up their browsers and pointing to your Web server's host name. If you're using round robin DNS resolution, the first client will resolve your host name and the DNS server will return the first IP address. Upon receiving the second request, your DNS server will hand out the second entry's IP address and the third client will get the third address. Voila! No one server gets all of the traffic.
There may come a time when you just want all traffic to go to the first resolved address. To make this happen, do the following:
- From the server on which you have DNS installed, go to Start | Administrative Tools | DNS.
- Right-click your DNS server's name and, from the shortcut menu, choose Properties.
- Select the Advanced tab.
- Deselect the check box next to "Enable Round Robin."
- Click OK.
Each client will now receive the first entry found for each request.
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