PTR is not a singleton

[peteeckel]

For some reason I always assumed that the record type PTR is a singleton type, i.e. there can be only one PTR record per name in a zone. For that reason, NetBox DNS checks that there are no two PTR records in any reverse zone that refer to the same address.

This, in fact, is not correct. NetBox DNS should allow multiple PTR records with the same name in a reverse lookup zone. Restricting PTR records to uniqueness is an unnecessary and incorrect limitation of the data NetBox DNS can keep.