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Re: lame delegations

  • From: Alex Kamantauskas
  • Date: Fri Aug 18 16:50:33 2000

On Fri, 18 Aug 2000, Gary E. Miller wrote:

> RFC 1912, Sec 2.1:
> " Make sure your PTR and A records match.  For every IP address, there
>    should be a matching PTR record in the domain.  If a
>    host is multi-homed, (more than one IP address) make sure that all IP
>    addresses have a corresponding PTR record (not just the first one).
>    Failure to have matching PTR and A records can cause loss of Internet
>    services similar to not being registered in the DNS at all.  Also,
>    PTR records must point back to a valid A record, not a alias defined
>    by a CNAME.  It is highly recommended that you use some software
>    which automates this checking, or generate your DNS data from a
>    database which automatically creates consistent data."
> I have yet to hear a convincing argument why this RFC should be
> ignored.  I have seen many problems when this is ignored.

 This raises a question that I've had for some time. This says that a "PTR
 record must point to a valid A record, not an alias defined by a CNAME".
 RFC 1035, Sec. 3.3.12 says that the PTRDNAME is a "<domain-name> which
 points to some location in the domain name space" and that "PTR records
 cause no additional section processing".  Since RFC 1035, Sec. 3.3 states
 that a <domain-name> is just a label, and says nothing that the label has
 to have a corresponding A record.  Since RFC 1912 is informational and
 does not update RFC 1035, it would seem that a PTR record does *not* have
 to point to a host that resolves.  

 No?  Am I getting lost in the fine print?  Am I missing a later RFC that
 clarifies this?

Alex Kamantauskas
[email protected]