Usage of A records for aliasing

[Kevin Darcy]

An A record isn't really an "alias", strictly speaking: it's a
name-to-address mapping. I assume you're referring to the use of
multiple A records to point to the same IP address (?) Off the top of my
head, the only reason I can think of to do this is if you want a name
which also happens to be a domain, e.g. foo.com to resolve to the same
address as some other name, e.g. www.foo.com. In this case, you can't
just create a CNAME, because then the CNAME would "hide" all of the
domain information (NS records, SOA records, etc.) for foo.com and your
nameserver will barf on it.

Generally, CNAMEs are preferred for the aliasing function because
a) they have less maintenance: if the underlying IP address changes,
then you only need to change the one A record, and all of the CNAMEs
which point to it automatically start returning the new address, and
b) it causes less confusion in terms of matching up A records with
PTR records: if a single address has 5 A records pointing to it, to
which of those names should the PTR point?


Hope that helps,


- Kevin

Chris Buchanan wrote:

> Would somebody be so kind as to explain the advantages of using
> A records for aliasing instead of CNAME records, and visa versa?
>
> --
> Chris Buchanan, B. Math
> http://www.undergrad.math.uwaterloo.ca/~csbuchan