CNAME only zone?

/dev/rob0 rob0 at
Fri Dec 9 18:21:35 UTC 2011

Please do not top-post. Thank you.

On Friday 09 December 2011 11:52:58 Lightner, Jeff wrote:
> "Also note that other workarounds will solve the same problem
> in a better way."
> Care to enlighten me as to what those workarounds would be?

Not knowing the exact situation puts me at a distinct handicap in 
trying to do so, but I can suggest some possibilities beyond what was 
suggested by Jan-Piet and Phil.

- A cron job to look up the desired name and nsupdate(8) the A
  record for when that address changes
- HTTP redirects, or just a redirect for to point to
  your desired CNAME target; *can* be a CNAME.
- Find different hosting.

> Also - why is it a registrar can do a CNAME only but we mere
> mortals can't?

Only approved registrars are allowed to update records in official 
top-level domains. You can make as many CNAME records as you like, 
playing by the rule that a CNAME cannot coexist with a record of the 
same name and any other RRtype.

Registrars are also bound by the reality of DNS. If you want a CNAME, 
they do not delegate the zone to you. They remove any NS records which 
had been in place for your zone, and your nameservers are no longer in 
use for that name. In fact by not being delegated, it ceases to be a 

> In fact documentation from Amazon (it is
> apparently their web store I've since learned) suggests doing it
> at registrar so I'll probably go that route but I'm wondering why
> it should work there but not on one of my delegated name servers.

Phil answered this, but to restate/repeat, a delegated zone *must* 
have SOA and NS records at the zone apex. Meaning: if 
is delegated, the parent com zone at a a minimum has NS records for, and your zone *must* contain SOA and NS records for

Those SOA and NS violate the rule that a CNAME cannot coexist with a 
record of the same name and any other RRtype.
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