This read-only octet string holds the interface name the CDP neighbor uses to identify the port on its own side of the connection, part of a remote-neighbor table row. It helps an admin trace cabling end-to-end by showing not just which local port a neighbor is on, but which port on the neighbor itself is used. A value like GigabitEthernet0/1 tells the admin exactly which interface on the far-end device to check or reconfigure.