What is LOS in WiFi Router?

LOS, or Loss of Signal, on a WiFi router or ONT (the box your fiber connection terminates into) refers to a state in which the device isn't receiving a signal on its fiber or WAN input.

It usually appears as a red LOS light on the device, indicating that the connection between your equipment and your ISP's network has been interrupted somewhere along the line.

This can happen for a few reasons: a loose or damaged fiber/WAN cable, a dirty or dislodged fiber connector, an outage on your ISP's end, a temporary sync issue after a power cut, or in some cases, account-related suspension from your ISP.

It's essentially your router or ONT telling you "I'm not getting a signal to work with," rather than a wifi problem on your local network.

Worth noting: LOS is also used in networking to mean Line of Sight, a direct, unobstructed path between a router's antenna and a receiving device, which affects wifi signal strength and range.

It's a completely different concept from Loss of Signal, but since both share the same acronym, it's easy to mix them up depending on context.

If you're troubleshooting a red light on your device, it's almost always Loss of Signal. If you're talking about wifi coverage or placement, it's Line of Sight.