[Gllug] DNS CNAME usage.

[Steve Nelson]

On 3/20/06, David Damerell <damerell at chiark.greenend.org.uk> wrote:
> On Monday, 20 Mar 2006, Steve Nelson wrote:
> >Your OP asked whether there would be a problem.
>
> The OP did _not_ ask if there would be a problem with a CNAME chain.

The OP asks:

"Does anyone have an opinion about CNAME usage and using a CNAME record
to refer to a canonical name that is not part of the current domain and
whether there should be problems associated with this?"

I read this to mean a CNAME pointing to another CNAME.  Reading back,
I see I read that wrongly.

> RFC 1034 section 3.6.2.

Yeah, I've read that before, and didn't think it amounted to an
explicit prohibition a CNAME pointing to a CNAME.

"Domain names in RRs which point at another name should always point at
the primary name and not the alias.  This avoids extra indirections in
accessing information.  For example, the address to name RR for the
above host should be:

    52.0.0.10.IN-ADDR.ARPA  IN      PTR     C.ISI.EDU

rather than pointing at USC-ISIC.ARPA.  Of course, by the robustness
principle, domain software should not fail when presented with CNAME
chains or loops; CNAME chains should be followed and CNAME loops
signalled as an error."

I was thinking along the lines of:

cat IN A  213.225.100.200
pussy IN CNAME cat
moggie in CNAME pussy

I appreciate that on reflection this doesn't assist the OP, but do you
think this is forbidden?

S.
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