10.7 A Nonrecursive Name Server


DNS on Windows 2000, 2nd Edition
By Matt Larson, Cricket Liu
Table of Contents
Chapter 10.  Advanced Features and Security

10.7 A Nonrecursive Name Server

By default, resolvers send recursive queries, and name servers do the work required to answer the queries. (If you don't remember how recursion works, refer to Chapter 2.) In the process of finding the answer to recursive queries, the name servers build up a cache of nonauthoritative information about other zones.

In some circumstances, it is undesirable for name servers to do the extra work required to answer a recursive query or to build up a cache of data. The root name servers are an example of these circumstances. The root name servers are too busy to spend extra effort to recursively find the answer to a request. Instead, they send a response based only on the authoritative data they have. The response may contain the answer, but it is more likely that the response contains a referral to other name servers. And since the root servers do not support recursive queries, they do not build up nonauthoritative data caches, which is good because their caches would be huge. [4]

[4] Note that a root name server doesn't normally receive recursive queries unless a name server's administrator configured it to use a root server as a forwarder, a host's administrator configured its resolver to use the root server as a name server, or a user pointed nslookup at the root server.

You can induce the Microsoft DNS Server to run as a nonrecursive name server by setting the NoRecursion Registry value to true. By default, the name server supports recursion, and this value is false.

If you choose to make one of your servers nonrecursive, do not configure any of your hosts ' resolvers to use it. While you can make your name server nonrecursive, there is no corresponding option to make your resolver work with a nonrecursive name server. [5]

[5] In general. Clearly, programs designed to send nonrecursive queries (or ones that can be configured to send nonrecursive queries, like nslookup ) would still work.

You can list a nonrecursive name server as one of the servers authoritative for your zone data (that is, you can tell a parent name server to refer queries about your zone to this server). This works because name servers send nonrecursive queries between themselves .

Do not list a nonrecursive name server as a forwarder. When a name server is using another server as a forwarder, it sends the query to the forwarder as a recursive query instead of a nonrecursive query.


DNS on Windows 2000
DNS on Windows 2000
ISBN: 0596002300
EAN: 2147483647
Year: 2001
Pages: 154

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