CName Terminology Question

[Barry Margolin]

In article <38F65908.B5E35509 at tmca.com.au>,
Stanley Liu  <stanley.liu at tmca.com.au> wrote:
>So what is the difference between the following set up:
>
>bar.com.      IN A 192.168.1.1
>foo.bar.com. IN A 192.168.1.1
>
>as compared to
>
>bar.com.      IN A        192.168.1.1
>foo.bar.com. IN CNAME bar.com.
>
>What if I query about foo.bar.com, is there any difference in the answer?  Under

No.

>what circumstances would I use the former and and under what
>circumstances would I
>use the latter?

You would use two A records if you needed to have NS or MX records pointing
to foo.bar.com, since they're not supposed to point to CNAME records.

I recommend using CNAMEs whenever it doesn't conflict with a restriction
against using CNAMEs, so that you don't have to have redundant entries.
The restrictions are that a name with a CNAME record can't have any other
records (this is why an SOA can't be a CNAME as well) and recorders that
point to other names can't point to CNAME records.

-- 
Barry Margolin, barmar at genuity.net
Genuity, Burlington, MA
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