snMSTrunkPortIndex 1.3.6.1.4.1.11.2.3.7.11.12.1.3.6.2.1.1

The primary port of a trunk group. For module with Gig ports, primary port is port 1, 3, 5, 7. For module with 10/100 ports, primary port is port 1, 5, 9, 13, 17, 21.