DNS on Windows Server 2003, 3rd Edition

How Many Name Servers?

We set up two name servers in Chapter 4. Two servers are as few as you’ll ever want to run and, depending on the size of your network, you may need to run many more. It is not uncommon to run four or more name servers, with one of them off-site. How many name servers are enough? You’ll have to decide that based on your network. Here are some guidelines to help out:

• Run at least one name server on each network or subnet you have. This removes routers as a point of failure. Make the most of any multihomed hosts you may have since they are (by definition) attached to more than one network.

• If you have a file server and some diskless nodes, run a name server on the file server to serve this group of machines.

• Run name servers near, but not necessarily on, large multiuser computers. The users and their processes probably generate a lot of queries and, as administrators, you will work harder to keep a multiuser host up. But balance their needs against the risk of running a name server—a security-critical server—on a system to which lots of people have access.

• Run one name server off-site. This makes your data available when your network isn’t. You might argue that it’s useless to look up an address when you can’t reach the host. Then again, the off-site name server may be available if your network is reachable but your other name servers are down. If you have a close relationship with an organization on the Internet—say another university or a business partner—they ...