What is the meaning of router lights? POWER, LOS, PON, WLAN, WAN
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Common Router Lights Explained (Power, LOS, PON, WLAN, LAN)
Routers and modems have small LED lights on the front that act like a health report for your internet connection. Understanding these lights helps you quickly figure out where the problem is when your internet stops working or becomes slow.
What Router Lights Tell You
Router lights show the status of power, the line from your internet provider, Wi‑Fi, and wired devices. When you know what each light means, you can tell whether the issue is inside your home (router, Wi‑Fi, cables) or outside (your ISP line).
Power Light
The Power light shows whether your router or modem is turned on and receiving electricity.
Solid green/white: The router is powered on and working normally.
Blinking during startup: The device is booting or installing an update; wait a couple of minutes.
Off or red/orange: There is no power or a hardware fault.
If the Power light stays off, check the power adapter at both ends, try another socket, and if it still does not turn on, the device may be faulty and need replacement.
LOS Light (Loss of Signal)
On fiber connections, LOS usually stands for “Loss of Signal” and appears on ONTs (fiber modems) or fiber routers.
Off: Fiber signal is normal; no loss detected.
Blinking or solid red: The device is not receiving a proper fiber signal.
If LOS is red or flashing:
Make sure the fiber cable is not bent sharply and is firmly connected.
Restart your ONT and router.
If LOS remains red, contact your ISP because the issue is likely on the line or at their end.
PON Light (Passive Optical Network)
PON shows whether your fiber device is properly registered and connected to your provider’s network.
Solid green: The ONT is authenticated and the fiber link is active.
Blinking green: It is trying to establish or register the connection.
Off or red: The device is not connected or not provisioned correctly.
If PON never becomes solid:
Restart the ONT and wait a few minutes.
Check all fiber connectors.
Ask your ISP to check if your line is activated and correctly configured.
WLAN Light (Wi‑Fi)
The WLAN (or Wi‑Fi) light shows the status of your wireless network.
Solid green/white: Wi‑Fi is turned on and broadcasting; your network name (SSID) should be visible.
Blinking: Wireless data is being transmitted (normal when you are browsing, streaming, etc.).
Off: Wi‑Fi is disabled or not working; only wired connections will work.
If WLAN is off but internet works via cable, enable Wi‑Fi from the router settings or press the Wi‑Fi button if your router has one. On dual‑band routers, make sure both 2.4 GHz and 5 GHz Wi‑Fi networks are enabled if you need them.
LAN Lights (Ethernet Ports)
LAN lights represent the Ethernet ports on the back of your router.
Solid green/white: A device is connected with a cable and the link is active.
Blinking: Data is being transferred between the router and that device.
Off: No active device is connected, or there is a cable/port/device problem.
If your computer has no internet and the LAN light is off:
Unplug and replug the Ethernet cable on both ends.
Try another LAN port on the router.
Test with another cable or another device to see which component is faulty.
Using Lights for Quick Troubleshooting
You can combine the meanings of these lights to quickly find the source of a problem:
Power solid, LOS red, PON off: Fiber signal problem outside your home; restart devices, then contact your ISP.
Power solid, PON solid, WLAN off: Internet is reaching your router, but Wi‑Fi is off; enable WLAN in settings or via button.
Power solid, WLAN and LAN normal, but no internet: The local network is fine; the issue is between your router and your ISP (line or configuration).
All lights normal but internet is slow: Could be congestion, Wi‑Fi interference, or too many devices; run a speed test and remove extra devices to test.
FAQ
Why is my router power light blinking?
A blinking power light usually means the router is starting up or updating firmware. If it keeps blinking for a long time and never becomes solid, restart it; if that does not help, there may be a firmware or hardware fault.
LOS light is red – what should I do?
A red LOS light almost always means the fiber signal is missing or unstable. After checking the cable and restarting the device, contact your ISP so they can test and repair the line.
WLAN light is on but I have no internet.
If the WLAN light is on, your Wi‑Fi network is working, but your internet connection may not be. Check the PON, LOS, or Internet/WAN lights; if they are red, off, or blinking strangely, the issue is with the connection from your router to the ISP.
LAN light is off even with a cable connected.
If the LAN light is off, the router does not detect an active device on that port. Try another cable, another port, and confirm the connected device is powered on and its network adapter is enabled.
