Chapter 26. Managing DNS
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| IN THIS CHAPTER
Computers on a network need to be found to be useful, which means we need to be able to identify each computer so we can connect to them and communicate with them. Most of today's networks use the Internet Protocol (IP), so each computer on these networks has a unique IP address to identify it. An IP address is a very large 32-bit number, but we have a shortcut method of displaying that number called the "dotted quad" address. The dotted quad form of the address is made of four 8-bit numbers separated by dots. For example, a computer with the address 3232250992 has the dotted quad form 192.168.60.112. It's easier to use and remember the dotted quad form of an IP address, but even then remembering a lot of numbers becomes quite difficult. The domain name system (DNS) enables you to allocate hostnames that are much easier to remember to these IP addresses. These names, such as fedora.redhat.com, are translated by DNS into the dotted quad IP address, saving time and memory! This translation process is called name resolution and is performed by software known as a resolver. For the average user, local configuration involves the DNS client, which queries a remote DNS server to exchange information. The DNS servers are typically maintained by Internet service providers (ISPs) and large corporate networks, although anyone can configure and run their own DNS server. All computers on networks need to have a properly configured DNS client. This chapter introduces DNS concepts and practice using Berkeley Internet Name Domain (BIND), the de facto standard DNS software for Unix. In this chapter, you learn some of the concepts that are basic to DNS and its functions, including how DNS structure information is stored, how DNS serves name information to users, and how name resolution actually works. You learn how to use BIND to configure nameservers and how to provide DNS for a domain. This chapter also teaches you some important techniques for keeping DNS functions secure, as well as some of the most important troubleshooting techniques for tracking down potential problems related to your DNS functions. If you are not going to be a DNS administrator, much of the information in this chapter will be of no practical use to you. That said, the knowledge of DNS that you can gain in this chapter might help you understand DNS problems that occur so you will realize that it is not your computer that is broken! You will also see how, after you register a domain name, you can obtain third-party DNS service so that you do not have to maintain a DNS server. Also, the commonly used DNS-related tools are explained with a focus on how they can be used to troubleshoot domain name resolution problems that you're likely to encounter. DNS is essential for many types of network operations, and especially so when providing connectivity to the outside world via the Internet. DNS was designed to make the assignment and translation of hostnames fast and reliable and to provide a consistent, portable namespace for network resources. Its database is maintained in a distributed fashion to accommodate its size and the need for frequent updates. Performance and bandwidth utilization is improved by the extensive use of local caches. Authority over portions of the database is delegated to people who are able and willing to maintain the database in a timely manner, so updates are no longer constrained by the schedules of a central authority. DNS is a simple but easily misconfigured system. Hostname resolution errors might manifest themselves in ways that are far from obvious, long after the changes that caused the errors were made. Such naming errors can lead to unacceptable and embarrassing service disruptions. An understanding of the concepts and processes involved in working with BIND will help to make sure that your experiences as a DNS manager are pleasant ones. |
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EAN: 2147483647
Pages: 361