djbdns is a collection of Domain Name System tools. It includes
software for all the fundamental DNS operations:

* DNS cache: finding addresses of Internet hosts. When a browser
  wants to contact www.hotwired.com, it first asks a DNS cache,
  such as djbdns's dnscache, to find the IP address of www.hotwired.com.
  Internet service providers run dnscache to find IP addresses
  requested by their customers. If you're running a home computer
  or a workstation, you can run your own dnscache to speed up your
  web browsing.

* DNS server: publishing addresses of Internet hosts. The IP address
  of www.hotwired.com is published by HotWired's DNS servers. djbdns
  includes a general-purpose DNS server, tinydns; network administrators
  run tinydns to publish the IP addresses of their computers. djbdns
  also includes special-purpose servers for publishing DNS walls
  and RBLs.

* DNS client: talking to a DNS cache. djbdns includes a DNS client
  C library and several command-line DNS client utilities. Programmers
  use these tools to send requests to DNS caches.

djbdns also includes several DNS debugging tools, notably dnstrace,
which administrators use to diagnose misconfigured remote servers.

Homepage:
https://cr.yp.to/djbdns.html
