The natural attacks of a creature with DR/x, bypass DR/x. Additionally, high enhancement bonuses bypass DR/ certain materials and alignments.
DR/ weapon type (bludgeoning, piercing, slashing) forcibly needs that kind of damage.
So far everything seems fine.
However, there are some powerful creatures with DR/alignment + material (typically, demons and devils). Would their natural attacks bypass DR/magic? It seems not to, according to RAW, but DR/magic is way "lesser" a characteristic than DR/alignment, so it seems rather strange to me if that is the case.
Thanks for any clarification!