[geeks] DNS: CN & A records

[Mike Meredith]

On Thu, 23 Jun 2005 11:41:44 -0400 (EDT), Kevin wrote:
> Regarding DNS configuration, i see some people using multiple A
> records as opposed to one A record and multiple CN records?  Is there
> any reason for this?

As in :-

dns0	IN A 148.197.254.1
mail	IN A 148.197.254.1 

?

You can't use CNAMEs on the right hand side of a resource record (i.e.
"port.ac.uk. IN NS dns0.port.ac.uk." would be invalid). Lazy hostmasters
(/me looks guilty) tend to avoid CNAMEs to avoid making stupid mistakes.

> I always thought you were supposed to have one A record per IP and
> then use CN records for additional aliases.

Nope. You can have as many A records pointing to an IP as you wish. In
theory you should have multiple PTR records pointing back to every name
that points to the IP :-

1.254.197.148.in-addr.arpa. IN PTR dns0.port.ac.uk.
1.254.197.148.in-addr.arpa. IN PTR mail.port.ac.uk.

In practice it isn't usually done, and pretty much nobody cares ...
except for a certain Greg who used to live on these lists.

(I'm deliberately ignoring IPv6)