Chapter 6: DNS	DNS Configuration 212

DNS Configuration

This section presents the following topics:

•DNS Overview

•DNS Configuration Examples

DNS Overview

The Domain Name System (DNS) is an Internet directory service providing mappings between human-readable domain names and numeric IP addresses. DNS mappings are recorded in resource records that are stored on name servers distributed throughout the Internet. A device needing to access a host across the Internet sends a DNS query to a name server. The name server consults its resource records and returns an answer with the IP address of the specified name.

The DNS system forms its own network on the Internet. If the requested record is not local to the consulted name server, the name server consults another name server, and so on, until the requested information is located and returned.

There are billions of resource records in the DNS system. To keep the data manageable, the records are divided into zones, which contain resource records for a DNS domain or subdomain.

The Vyatta system supports three main DNS-related features:

•System DNS

•Dynamic DNS

•DNS Forwarding

System DNS

In system DNS, you define the list of name servers that the Vyatta system can use to resolve hostnames to IP addresses. This list is created using the system name-server command. (The system name-server command is described in the Vyatta Basic System Reference Guide; for your convenience, an example of system DNS is provided in this chapter in “Example 6-1 Configuring static access to a DNS name server.”)

Dynamic DNS

Originally, DNS mappings were statically specified in “zone files,” which were periodically loaded onto DNS servers. This worked reasonably well at a time when most hosts were configured with static IP addresses. However, since the 1990s, many

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