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Sidewinder G2 6.1.2 Administration Guide - Glossary of Technical ...

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Chapter 11: DNS (Domain Name System)<br />

What is DNS?<br />

What is DNS? The domain name system (DNS) is a service that translates host names to IP<br />

addresses, and vice versa. DNS is necessary because while computers use a<br />

numeric addressing scheme to communicate with each other, most individuals<br />

prefer to address computers by name. DNS acts as the translator, matching<br />

computer names with their IP addresses.<br />

312<br />

Much <strong>of</strong> the traffic that flows into and out <strong>of</strong> your organization must at some<br />

point reference a DNS server. In many organizations this server resides on a<br />

separate, unsecured computer. The <strong>Sidewinder</strong> <strong>G2</strong> provides the additional<br />

option to host the DNS server directly on the <strong>Sidewinder</strong> <strong>G2</strong>, eliminating the<br />

need for an additional computer.<br />

The <strong>Sidewinder</strong> <strong>G2</strong> <strong>of</strong>fers two main DNS configurations: Transparent DNS and<br />

<strong>Sidewinder</strong>-hosted DNS. The sections below explain each configuration<br />

method.<br />

Note: An excellent source <strong>of</strong> information on DNS is the Internet S<strong>of</strong>tware<br />

Consortium Web site at www.isc.org. Some background information is also<br />

provided in the <strong>Sidewinder</strong> <strong>G2</strong> installation documentation. The book DNS and<br />

BIND, by Albitz & Liu (O’Reilly & Associates, Inc.) is also a popular reference.<br />

About transparent DNS<br />

Transparent DNS represents a simplified DNS configuration. When transparent<br />

DNS is configured for the <strong>Sidewinder</strong> <strong>G2</strong>, DNS traffic passes transparently<br />

through the <strong>Sidewinder</strong> <strong>G2</strong> using a proxy. The <strong>Sidewinder</strong> <strong>G2</strong> uses proxy rules<br />

that pass all DNS traffic by proxy to its appropriate burb. DNS requests are<br />

then handled by the remote servers. Other machines do not “see” the<br />

<strong>Sidewinder</strong> <strong>G2</strong>, which means there is minimal disruption to your current DNS<br />

configurations throughout your network.<br />

Configuring transparent DNS requires specifying the IP address <strong>of</strong> one or more<br />

remote DNS servers. (Alternative server addresses may be used for<br />

redundancy.) If a customer is using NAT through the <strong>Sidewinder</strong> <strong>G2</strong>, they<br />

should also have an additional DNS server on the outside <strong>of</strong> their network. The<br />

external DNS server handles the external zones <strong>of</strong> your network and its<br />

addresses. This configuration allows you to control which addresses are visible<br />

to the outside world.<br />

Note: Transparent DNS is designed for simple DNS configurations. Complex DNS<br />

configurations may require DNS services to be hosted directly on the <strong>Sidewinder</strong><br />

<strong>G2</strong>.

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