Is Fajr prayer an obligatory act or a Sunnah? And is Subh prayer an obligatory act or a Sunnah?

The Fajr prayer is an obligatory duty by the consensus of the Muslim nation. Whoever denies its obligation has committed an act of disbelief, because it is known to be a necessary part of the religion. There is also a supererogatory prayer associated with it, which consists of two rak'ahs before it.