This read-write bitmap, DURABLE across reboots, indicates which ports' traffic is being copied to the monitor port, using the same bit-per-ifIndex encoding as the interface table (for example, a value of 5 marks bits for ports 1 and 3). An admin configures this to choose exactly which ports get mirrored to the monitor port defined by cpqn52nnPortMonitorIfIndex. For example, setting this bitmap to select ports 1 and 3 lets a single analyzer on the monitor port capture traffic from both of those source ports simultaneously.