Bind and dns pdf

However, it relies completely on its forwarders; it doesn't try to contact other servers to find out information if the forwarders don't give it an answer. You must have the forwarders line in the conf or boot file. In the process of finding the answer to recursive queries, the name server builds up a cache of nonauthoritative information about other domains. In some circumstances, it is undesirable for name servers to do the extra work required to answer a recursive query or to build up a cache of data.

The root name servers are an example of one of these circumstances. The root name servers are so busy that they should not be spending the extra effort to recursively find the answer to a request. Instead, they send a response based only on the authoritative data they have. The response may contain the answer, but it is more likely that the response contains a referral to other name servers.

And since the root servers do not support recursive queries, they do not build up a cache of nonauthoritative data, which is good because their cache would be huge. If you choose to make one of your servers nonrecursive, do not list this name server in any host's resolv.

While you can make your name server nonrecursive, there is no corresponding option to make your resolver work with a nonrecursive name server. Clearly, programs designed to send nonrecursive queries, or that can be configured to send nonrecursive queries, like nslookup, would still work.

You can list a nonrecursive name server as one of the servers authoritative for your zone data i. This works because name servers send nonrecursive queries between themselves.

Do not list a nonrecursive name server as a forwarder. When a name server is using another server as a forwarder, it sends the query to the forwarder as a recursive query instead of a nonrecursive query. You can attempt to find an administrator to fix the problem.

The chapter also includes a section on special considerations that may arise because IPv6 connectivity is not yet pervasive. This chapter explains the DNS64 transition technology, which allows clients with IPv6-only network stacks to communicate with IPv4 servers.

This chapter describes how to use the common nslookup and dig troubleshooting tools to look up the IPv6 addresses of a domain name or reverse-map an IPv6 address to a domain name. Indicates menu titles, menu options, menu buttons, and keyboard accelerators such as Alt and Ctrl.

Indicates new terms, URLs, email addresses, filenames, file extensions, pathnames, directories, and Unix utilities. Indicates commands, options, switches, variables, attributes, keys, functions, types, classes, namespaces, methods, modules, properties, parameters, values, objects, events, event handlers, XML tags, HTML tags, macros, the contents of files, or the output from commands. This book is here to help you get your job done.

In general, you may use the code in this book in your programs and documentation. For example, writing a program that uses several chunks of code from this book does not require permission. Answering a question by citing this book and quoting example code does not require permission. We appreciate, but do not require, attribution. An attribution usually includes the title, author, publisher, and ISBN. Zone files contain information about the portion of a domain for which they are responsible.

This could be the whole domain sun. In our example, the hp. The first one, support. The second one though, pr. The hp.

If anyone requires more information on support. So you see that even though support. On the other hand, the Sun. This zone is loaded by the authoritative name servers. Keeping things simple, it's a program you download www.

The download is approximately 4. Untarring and compiling BIND is a pretty straight forward process and the steps required will depend on your Linux distribution and version. If you follow the instructions provided with the download, you shouldn't have any problems. For simplicity purposes, we assume you've compiled and installed the BIND program using the provided instructions. No matter what Linux distribution you have, the file structure is pretty much the same.

When all of your configuration and zone files have no errors in them, you should be ready to restart the BIND service. In most environments, it is a good idea to set up a secondary DNS server that will respond to requests if the primary becomes unavailable.

Luckily, the secondary DNS server is much easier to configure. Save and exit named. Define slave zones that correspond to the master zones on the primary DNS server. If you defined multiple reverse zones in the primary DNS server, make sure to add them all here:.

Now you must configure your servers to use your private DNS servers. Add the following lines to the file substitute your private domain, and ns1 and ns2 private IP addresses :. Then add the following lines to the TOP of the file substitute your private domain, and ns1 and ns2 private IP addresses :. Use nslookup to test if your clients can query your name servers. For example, we can perform a forward lookup to retrieve the IP address of host1. The output of the command above would look like the following:.

If all of the names and IP addresses resolve to the correct values, that means that your zone files are configured properly. If you receive unexpected values, be sure to review the zone files on your primary DNS server e. Your internal DNS servers are now set up properly!

Now we will cover maintaining your zone records. Now that you have a working internal DNS, you need to maintain your DNS records so they accurately reflect your server environment.

Whenever you add a host to your environment in the same datacenter , you will want to add it to DNS. Here is a list of steps that you need to take:. If you remove a host from your environment or want to just take it out of DNS, just remove all the things that were added when you added the server to DNS i. This makes configuration of services and applications easier because you no longer have to remember the private IP addresses, and the files will be easier to read and understand.

Also, now you can change your configurations to point to a new servers in a single place, your primary DNS server, instead of having to edit a variety of distributed configuration files, which eases maintenance.

Once you have your internal DNS set up, and your configuration files are using private FQDNs to specify network connections, it is critical that your DNS servers are properly maintained. If they both become unavailable, your services and applications that rely on them will cease to function properly. This is why it is recommended to set up your DNS with at least one secondary server, and to maintain working backups of all of them.

Software Engineer DigitalOcean.