CNAME VS A

[Kevin Darcy]

Scott.Wiseman wrote:

> what is the difference?
>
> bigt.movie.edu    IN    A    192.168.1.1
> bigdah.movie.edu    IN CNAME bigt.movie.edu
>
> VS
>
> bigdah.movie.edu    IN    A    192.168.1.1

The CNAME provides an extra level of indirection. This can be useful if
you have a whole bunch of aliases -- possibly in different zones -- to
one A record, say, and you only want to make a change in one place if
the address changes, or if the "real" record is to be maintained by a
different organization than the one maintaining the alias name. Also,
CNAMEs can help disambiguate forward/reverse DNS, e.g. you have 10 names
that all must resolve to the same address, to which one of those 10
names does the address reverse-map? You can solve this by making 9 of
those names aliases to the "real" name, to which the address
reverse-maps.

Also, some programs -- like sendmail -- care about the difference
between an alias and a "real" name.


- Kevin