This read-write value indicates which physical line the logical port is associated with, drawn from up to 8 lines on a multi-line card, though T3 cards support only a single line. An administrator sets this when creating a new logical port to bind it to the correct physical T1/E1 line on the card. For example, on an 8-port E1 card, setting cesPortLineNum to 3 for a newly added port ties that port's DS0 timeslot allocation to physical line 3 specifically.