Answered by Shaykh Yusuf Weltch
Question: As our beloved prophet (peace and blessings be upon him ) said the one who prays two Sunnah rakats of fajr will receive great rewards. My question is the two rakats Sunnah prayer of fajr should be prayed after azaan or before the azaan of fajr?
Answer: In the Name of Allah, the Most Merciful and Compassionate
As soon as the Fajr time has entered, regardless of whether the adhan has been called or not, one can pray the sunna prayers.
[Shurunbulali, Maraqi al -Falah]
Hope this helps
And Allah knows best
[Shaykh] Yusuf Weltch
Checked and Approved by Shaykh Faraz Rabbani