This integer, 1 to 65535, is the cost this ATM port contributes to the total path cost of any spanning-tree path toward the root bridge that passes through it. STP uses accumulated path cost to pick the lowest-cost path to the root, so an admin can tune this value to bias which links are preferred when redundant paths exist. Lowering the path cost on a high-bandwidth ATM trunk, for example to 10 versus a default of 100 on a slower link, makes STP favor that trunk as part of the active topology.