Multiple PTRs for the same IP

Fr34k freaknetboy at
Fri Jan 26 17:36:16 UTC 2007

Hello All,

I'm trying to find something "official" that states, or explains, why multiple
PTRs for the same IP are not a very good idea.

Let me explain what I am talking about, and where I am hoping to go with it.

In previous discussions on this topic, folks have mentioned things like:
 - most utilities will only use the first PTR returned in a query. So, why have
 - many PTRs may require TCP, rather than UDP, query traffic. This may cause
issues if UDP is expected/enforced (or why initiate unnecessary overhead)
 - many PTRs may cause confusion when doing an rDNS check on a hostname (eg.
they may not necessarily match in a round-robin scenario with multiple PTRs --
counter productive?)

My google searches find similar blogs that agree that multiple PTRs are a bad
One blog even says it is a "violation" to do so, but without reference to
back this claim.

Another tool says that while more than one PTR record for an IP is "legal", but
it suggests to use only on PTR record for reasons pointed out above.

While all of the above is excellent feedback from DNS gurus, I have been unable
to find anything "official" to refer an upper management audience to on this

Does anyone know of an RFC that discusses this (hopefully, in our favor that
multiple PTRs for the same IP is not a good thing).
Some other similar reputable source, perhaps, I can reference?

TIA -- Chris

I hope not to offend anyone for the feedback on this topic thus far.
That is not my intent.
I am looking for something to support policy. We all know that game, right?
I hope that is understood.

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