Selects, as a bitmap of ports (PortList), which ports should have their currently learned dynamic MAC addresses converted into static, locked entries ('frozen'). The source MIB's own DESCRIPTION field for this object is empty, so this reading is inferred from the object's name, its SYNTAX/enumeration, and its position in the MIB tree rather than vendor prose. An admin uses this to snapshot the MAC addresses currently seen on a set of ports and lock them in place, so no new/different device can use those ports afterward without reconfiguration.