This counter reports how many of the remote connections in this port's LLDP remote systems table were detected purely from MAC addresses learned in the switch's forwarding database for this port, rather than from any LLDP message. Administrators use it to see how many connected devices lack LLDP support entirely and were only discovered via passive MAC learning. For example, a high FDB entry count alongside a low IEEE entry count on the same port indicates most connected devices on that segment don't support LLDP.