A record of domain name must be name server ?

Mark Elkins mje at posix.co.za
Thu Sep 11 07:45:35 UTC 2014


On Wed, 2014-09-10 at 18:13 -0400, Kevin Darcy wrote:
> No, what I'm saying is that if
> 
> example.com owns an A record 203.0.113.48, and
> www.example.com owns an A record 203.0.113.48, then
> 
> where does 48.113.0.203.in-addr.arpa point?
> 
> Some people will point it at example.com, some will point it at 
> www.example.com. What you get is a mish-mosh. No consistency.

Although I prefer the use of a CNAME solution (CNAME www.example.com to
example.com), in the case of separate A (and AAAA) records, one could
point the reverse to both names. Nothing wrong with a PTR record having
more than one answer. There is then no inconsistency, just choice. After
all, pretty much every NS record has at least two Right-Hand-Sides
(Answers)....


> If, on the other hand, www.example.com is a CNAME to example.com, then 
> it's crystal clear where the reverse record will point -- example.com. 
> There is no ambiguity or option for inconsistency.
> 
>      - Kevin
> 
> On 9/10/2014 5:48 PM, Eliezer Croitoru wrote:
> > Hey Kevin,
> >
> > This is not an issue at all.
> > A PTR is different then a "A" record and can be used by two reverse 
> > domain names and only the owner of the IP addresses space can define 
> > them.
> > I am not sure if two PTR records for two domains will be applied to 
> > one IP but it is possible for two IP addresses to have the same PTR.
> >
> > Can we even use a CNAME as a PTR???
> >
> > Eliezer
> >
> > On 09/11/2014 12:37 AM, Kevin Darcy wrote:
> >> Also, have you considered the forward/reverse ambiguity that arises when
> >> multiple owner names resolve to the same address? To which of those
> >> names does the PTR point?
> >>
> >>      - Kevin
> >
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-- 
Mark James ELKINS  -  Posix Systems - (South) Africa
mje at posix.co.za       Tel: +27.128070590  Cell: +27.826010496
For fast, reliable, low cost Internet in ZA: https://ftth.posix.co.za
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