Openreach ONT Guide

May 16, 2024

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What do the lights on my Openreach ONT mean?

Different router types

If you have a Ultrafast Broadband (FTTP) connection with City communications you will likely have an Openreach modem (or ONT) installed. This modem or ONT connects to a fibre optic cable, which runs directly to your property and allows you to access our fibre network for broadband and voice.

There are a few different type of Openreach modem (or ONT). They will all do the same job, but the type and number of lights differs between devices.

PON and LOS lights

PON solid green – The fibre optic link to your local Openreach exchange is working and recognises your Openreach fibre modem (or ONT).

Check that the physical connection at both ends of the cable between the Openreach fibre modem and router. Try a new ethernet cable if required.

PON flashing and LOS off – Openreach fibre modem (or ONT) is communicating with the exchange for your service verification.

Wait until light turns solid green.

PON off, or PON and LOS both flashing – Your bibre optic link is not connected or there’s a problem between your property and the local exchange.

Check that the thin white fibre optic cable coming into your Openreach fibre modem (or ONT) is correctly inserted and not showing any signs of damage. Turn the Openreach fibre modem’s (or ONT) power off, then back on and wait 5 minutes for the Openreach fibre modem (or ONT) to attempt to reconnect.


No light – The Openreach fibre modem (or ONT) is off.
Check the mains plug is in.

Green – If the light is green the Openreach fibre modem (or ONT) is on.


Lights on – There is a Ethernet connection between your Openreach fibre modem (or ONT) and your router.

Lights blinking – Data is being transmitted through the port.

Lights off – Ethernet cable to router is not inserted or broken.
Check the cable connection at both ends. Try a new Ethernet cable if needed.

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