If you want to reduce network traffic for DNS and improve DNS lookup, one solution is to create a caching DNS forwarder on your network. A caching-only DNS server receives queries from clients, performs the queries against other name servers, caches the results, and returns those results to the client.
It then returns subsequent queries for the specified host from the cache instead of submitting them to an external server. This reduces outgoing DNS traffic and speeds up name resolution.
You can set up a caching-only server by configuring the DNS service with one or more forwarders, which are upstream DNS servers to which the local DNS server will forward queries (essentially acting as a DNS client).
You can configure the DNS service to work with forwarders either nonexclusively or exclusively. In nonexclusive mode, the DNS server checks its cache for the host. If the lookup fails, it forwards the query to the specified forwarder. If that query fails, the DNS server attempts to resolve the query on its own through the root servers.
In exclusive mode, the DNS service also checks its cache. If the lookup fails, it forwards the query to the forwarder.
If the upstream servers fail the query, the DNS server doesn't attempt resolution on its own; instead, it fails the query to the client. A DNS server acting in exclusive mode with a forwarder is a caching-only slave.
To configure forwarding, follow these steps:
- Open the DNS console, right-click the server, and choose Properties.
- On the Forwarders tab, choose Enable Forwarders, and add the IP addresses of the upstream DNS servers to which you want to forward queries.
- If you want the DNS service to work in exclusive mode, select the Do Not Use Recursion option.
- Click OK to apply the change.
Keep in mind that restarting the server will clear the DNS cache, so a caching-only server works best when it's been running for an extended period of time.
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