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[02] WHAT ARE THE DIFFERENT DNS RECORD TYPES?
This is a pretty quick and basic description. The most
important records are the A, MX and CNAME. You can probably
figure out how the DNS database entry works.
SOA Start Of Authority. Is probably the most complicated
portion of the DNS database to understand. SDF takes
care of this record for you.
A Address record. The IP address for a host or domain.
MX Mail Exchanger. The host who handles mail for your
domain/hosts. There is a numeric value before the
MX host to specify preference (typically 75 for
a primary, and 100 for a secondary)
CNAME Canonical Name - an equivilent host name.
A typical database (without the SOA) might look like this:
$ORIGIN mydomain.org.
foo IN A 10.0.0.1
IN MX 75 foo.mydomain.org.
IN MX 100 mail.anotherhost.org.
bar IN CNAME foo.mydomain.org.
Notice that the "." at the end of text is of importance.
the $ORIGIN is a tag in the database, which tells the nameserver
that all information following needs to have 'mydomain.org.'
appended to the initial tag (id est, foo.mydomain.org. instead
of just 'foo').
In the above example, host 'foo' has an address of 10.0.0.1 and
its favourite mail exchanger is itself. In the event that it
is unavailable, its second favourite mail exchanger is
'mail.anotherhost.org' which lives outside of this database.
Host 'bar' in basically just an equivilent name for 'foo' .. although
you could of just had another A and MX records for 'bar', this is
the most efficient and clean way to build your database.