> se puede mirar si ha habido un corte en la linea
Mira donde te dice el anterior mensaje el bocadepez
Y si quieres ver si se había cortado "físicamente" la línea, si tienes acceso root puedes mirar en el dmesg.
Como referencia, esto es lo que sale después de desconectar (y reconectar) el cable de fibra óptica:
[19:44:13.982598] ===GPON ALARM OFF ( E_GPON_ALARM_LOF )===
[19:44:13.982607]
[19:44:14.079082] mii1: link up, full duplex, speed 1 Gbps
[19:44:14.090545] br0: port 7(nbif0) entered disabled state
[19:44:14.522133] <3>GPON OMCC already exsits
[19:44:14.526160] ===GPON ALARM ON ( E_GPON_ALARM_LOS )===
[19:44:14.526166]
[19:44:14.622515] mii1: link up, full duplex, speed 1 Gbps
[19:44:14.627985] <3>GPON OMCC already exsits
[19:44:14.631969] ===GPON ALARM ON ( E_GPON_ALARM_LOF )===
[19:44:14.631975] ===GPON ALARM OFF ( E_GPON_ALARM_LOS )===
[19:44:19.534921] ===GPON ALARM OFF ( E_GPON_ALARM_LOF )===
[19:44:19.540179] ===GPON ALARM OFF ( E_GPON_ALARM_LOF )===
[19:44:23.502988]
[19:44:24.642240] mii1: link up, full duplex, speed 1 Gbps
[19:44:24.821306] <3>GPON OMCC already exsits
[19:44:24.826860] br0: port 7(nbif0) entered forwarding state
[19:44:24.832239] br0: port 7(nbif0) entered forwarding state