A record of domain name must be name server ?
kcd at chrysler.com
Thu Sep 11 15:27:59 UTC 2014
Depending on implementation, a PTR RRset with multiple
-- 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
-- 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)
So, although the standards allow multiple RRs, in practical terms, it
only makes sense for a PTR RRset to contain a *single* RR.
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 188.8.131.52.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
>> 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
>>> 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???
>>> 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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