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

4.2 RR Format

Names in the database must start on the first position. If the first character in the line is a space, the name from the previous line is used. A file consists of RRs (Resource Records), listed in Table 2.1.

4.2.1 SOA Records

The Start Of Authority (SOA) record determines the name server that is an authoritative source of information for the particular domain. There is always only one SOA record in the file, and it is placed at the beginning of the file of authoritative resource records.

Example 1: The record for the server of the zone:

@ IN SOA (
1 ;Serial
86400 ;Refresh after 24 hours
600 ;Retry after 5 min.
120960 ;Expire after 2 weeks
86400) ;Minimum TTL of 1 day

The explanation of the code is as follows:

  • The name must start immediately on the first position of the line and must have a dot at the end. It specifies the name of a zone. Usually @ is used instead of the name of the zone, which means the name of the zone should...