Address Record (A)

Address Record (A)

This record is one of the simplest RR’s and perhaps the most common.
Its purpose is to match a host name to an IP address. The Pointer record
(PTR) does the opposite, mapping an IP address to a host name. An
example of an A record in given below:
dns0 IN A 172.30.21.45
Mail Exchange Record (MX)
The MX record specifies a mail exchange server for a DNS domain. The
fields are similar to that of the NS record except there is an extra
numerical value, the mail server priority value. This indicates which
mail server should be attempted first in the situation where more than
one exists for a domain. The server with the lowest priority should be
attempted first. In the following example, showing the MX records for
the development domain, mailserver1 should be tried first, then
mailserver2 and finally mailserver3.
development.example.com IN MX 0 mailserver1.development.example.com
development.example.com IN MX 10 mailserver1.development.example.com
development.example.com IN MX 17 mailserver1.development.example.com
Further Information
For more information on the topics covered so far in this module,
consult RFC 1034, downloadable from the Internet Engineering Task
Force homepage (www.ietf.org).