Book Image

DNS in Action

By : CP Books a.s.
Book Image

DNS in Action

By: CP Books a.s.

Overview of this book

The Domain Name System is one of the foundations of the internet. It is the system that allows the translation of human-readable domain names into machines-readable IP addresses and the reverse translation of IP addresses into domain names. This book describes the basic DNS protocol and its extensions; DNS delegation and registration, including for reverse domains; using DNS servers in networks that are not connected to the internet; and using DNS servers on firewall machines. Many detailed examples are used throughout the book to show perform various configuration and administration tasks.
Table of Contents (16 chapters)
DNS in Action
About the Authors
Country Codes and RIRs

10.3 Dual DNS

If we want to have separate zones for both the Internet and intranet, we have to keep them on two separate computers (since they have the same domain name). The aim of dual DNS is to run the primary name server of the domain of both the Internet and intranet on just one computer if it is a question of money. While in big companies many different servers are run on the intranet, which enables the operation of separate name servers, small companies would often not wish to install another computer just to run the name server.

But how does a dual DNS work? Two name servers are run on the firewall (two processes). Each of them is run on a different port. The following figure shows the Internet name server being run on port 7053, while the intranet name server is run on port 8053:

Figure 10.5: Dual DNS

It is improbable that the usual client would use a port other than port 53, since they would not be aware of the existence of ports 7053 and 8053.

A DNS proxy is run on the...