One must enter into the state of Ihraam before passing the miqaat boundary.
Miqaat is the outer boundary from where those wishing to perform Hajj or Umrah must enter into the state of Ihram.
5 Boundaries
Dhul Hulaifah: north of Makkah
Al-Juhfah/Rabigh: north west of Makkah. (This is applicable to those who come from the west)
Yalamlam- south east of Makkah.
Qarn al-Manazil: east of Makkah.
Dhat al-Iraq: North east of Makkah in the direction of Iraq.