Chapter 8: BIND

Overview

DNS, or the Domain Name System, is absolutely vital to the functioning of the Internet. In fact, though you rarely interact directly with the DNS the Internet as we know it could not exist without its constant presence. DNS associates, or binds, host names and domain names to IP addresses and thus allows you to type http://www.swelltech.com instead of the much less memorable IP 216.40.244.74.

Further, it makes it possible for mail servers to easily locate the correct host to send mail to for a given domain, the correct administrative contact when strange things are originating from the domain, and more. But for our purposes, as ordinary system administrators, all we need to really keep in mind is that BIND is our method of providing DNS information for our network. It will provide information to our local users when their client applications need to access various sites by name. And it will provide information to clients (primarily other DNS servers acting as DNS clients in order to fetch the correct information for their clients) on the Internet at large in order to advertise to the world how host names on our network can be reached. Think of it as a fancy telephone book, or even better, a telephone operator, for networked computers. The client computer has a name, but needs the number in order to reach it across the vast Internet. So it contacts the DNS server and asks for the number, and BIND is happy to do its best to return the correct number.

Every host on a TCP/IP network has an IP address. This address must be unique for the network on which the address is routable. So, every host that is accessible via the Internet has a unique IP address that may, theoretically, be reached from anywhere else on the Internet. Because these addresses are doled out, roughly, according to physical location on the network, and because routers keep up with which other routers have access to which subnets, this simple number is all that is needed for your computer to establish a connection with any other computer on the Internet in seconds. Unfortunately the topic of routing on the Internet falls quite outside of the scope of this document, as Webmin is not designed to manage routers or the more complex routing features of Linux, FreeBSD, and the other operating systems that are supported.