The Open Road: Alternative Nameservers - PowerDNS
PowerDNS is an authoritative-only nameserver. This means that it will answer queries about zones that it is responsible for, but it won't attempt to find information on another zone/domain. For example, if you set up PowerDNS to handle "yourdomain.com," it won't answer queries for "mydomain.com" or "bobsdomain.com". This means that you don't have to worry about a poorly configured (or maliciously configured) server polluting your nameserver's cache. It can use a number of database backends or a BIND-type named.conf to store records. Interestingly, it also includes a built-in Web server to allow you to check out performance information and statistics in realtime.
PowerDNS also supports IPv6 and queries over UDP, but I won't cover the IPv6 features here since the protocol is still so seldom used. I also will not cover the UDP stuff specifically.
Interestingly, the software was at one time a commercial offering, but the folks who maintain PowerDNS decided that it was better to try to sell support for PowerDNS than to try to sell licenses. This is a pretty recent development; the company released the source under the GPL last November. They also sell a service using PowerDNS for companies to manage their DNS for domains, mail, and Web redirection, which you can find at PowerDNS Express.
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