Featured Article — Windows Server Configure a caching-only DNS forwarder
When 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. Subsequent queries for the specified host are returned from the cache rather than submitted to an external server, reducing outgoing DNS traffic and speeding 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, and if the lookup fails, forwards the query to the specified forwarder(s). 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 checks its cache, and if the host isn't cached, forwards the query to the forwarder. If the upstream servers fail the query, the DNS server does not attempt resolution on its own, but instead fails the query to the client. A DNS server acting in exclusive mode with a forward is called a caching-only slave.
To configure forwarding, open the DNS console, right-click the server, and choose Properties. On the Forwarders tab, choose Enable Forwarders and then add the IP addresses of the upstream DNS servers to which queries will be forwarded. If you want the DNS service to work in exclusive mode, check the Do Not Use Recursion option. Then, click OK to apply the change.
Note that the DNS cache is cleared when the server is restarted, so a caching-only server works best when it has been up for an extended period of time. |
