On Thu, 2014-09-11 at 11:27 -0400, Kevin Darcy wrote: > Mark, > Depending on implementation, a PTR RRset with multiple > records either > > -- only ever gets answered with the "first" record of the set (in > which case the second and subsequent records of the set are just a > waste of space), or > -- answers in a random, cyclic and/or round-robin fashion (in which > case, the results are non-deterministic from the standpoint of a > client, and this can cause problems and/or confusion)
Last time I checked, ALL matching records are returned as a single Resource Record Set - (and in the case of DNSSEC - covered with a single signature). What the receiver does with it is up to that receiver... as you say - some of the information may be discarded. > So, although the standards allow multiple RRs, in practical terms, it > only makes sense for a PTR RRset to contain a *single* RR. I would still disagree. When there is forward<-->reverse checking, one may need the complete answer. I certainly have some processes that do an exhaustive check. - Kevin > > On 9/11/2014 3:45 AM, Mark Elkins wrote: > > > 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 > > > > _______________________________________________ > > > > Please visit https://lists.isc.org/mailman/listinfo/bind-users to > > > > unsubscribe from this list > > > > > > > > bind-users mailing list > > > > bind-users@lists.isc.org > > > > https://lists.isc.org/mailman/listinfo/bind-users > > > > > > > > > > > > > > > _______________________________________________ > > > Please visit https://lists.isc.org/mailman/listinfo/bind-users to > > > unsubscribe from this list > > > > > > bind-users mailing list > > > bind-users@lists.isc.org > > > https://lists.isc.org/mailman/listinfo/bind-users > > > > > > _______________________________________________ > > Please visit https://lists.isc.org/mailman/listinfo/bind-users to > > unsubscribe from this list > > > > bind-users mailing list > > bind-users@lists.isc.org > > https://lists.isc.org/mailman/listinfo/bind-users > > _______________________________________________ > Please visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe > from this list > > bind-users mailing list > bind-users@lists.isc.org > https://lists.isc.org/mailman/listinfo/bind-users -- Mark James ELKINS - Posix Systems - (South) Africa m...@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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