Section 2, Task 1: Customize and Verify Your Test PDB
Prerequisite 4:
If you want to monitor line utilization for full-duplex
lines, you know the host name and instance number of each full-duplex
interface, if any, on your network.

For example, you would know something like this: the number 2 interface on and the number 4 interface on are full-duplex, and these are the only full duplex interfaces.