This read-only InterfaceIndex reports the ifIndex of the remote port on the neighboring device, noting there may not be an IP interface directly associated with that port. An administrator uses this to identify exactly which interface on the neighboring device is connected to the local port, essential for building accurate physical topology diagrams. For example, when mapping which switch port on a neighboring device connects to a given local uplink port, the admin reads this remote ifIndex value from the neighbor table entry.