Full fibre equipment: the ONT and your router

On the Openreach network, the fibre comes from a nearby pole or an underground duct to a small external junction box on an outside wall. Openreach gives its size as 15cm x 13cm. A small cable then runs through a hole drilled in the wall to the Optical Network Terminal (ONT) on the inside.

Openreach lists the equipment it may leave inside your home as:

• The ONT, which Openreach describes as a white box. Zen says it is labelled Openreach and is usually mounted on a wall on the ground floor.
• A Power Supply Unit (PSU), which powers the ONT from a mains socket. If it is unplugged, your broadband stops working.
• Internal fibre cabling and wall fittings between the entry point and the ONT.

Your router is the fourth piece. It normally comes from your broadband provider rather than Openreach, and it is what gives you Wi-Fi.

ISPreview reports that Openreach uses ONTs from several suppliers, including ADTRAN, Nokia, Zyxel and Sercomm, so yours may look different from a neighbour's.

How other full-fibre networks do it

• Gigaclear fits an external wall box and an internal wall-mounted box, drilling a new access hole.
• Ogi mounts its indoor and outdoor connection boxes back to back on a ground-floor outside wall, linked by a short cable through a small hole. Your router plugs into the indoor connection box.
• Community Fibre drills a small 6-8mm hole and wall-mounts a fibre socket, a modem and a mesh Wi-Fi router. It typically places them within 10 metres of where the fibre enters.
• Hyperoptic, on its own network, connects its Hyperhub router by Ethernet to a Hyperoptic wall socket or a fibre converter, depending on the set-up. It has announced plans to sell over Openreach too, but we found no launch as of 8 October 2026.

See our Gigaclear, Ogi, Community Fibre and Hyperoptic pages for each network's current offers.

The ONT's job is translation. Fibre carries your broadband as light; the ONT turns that into an ordinary wired network connection (Ethernet) that a router can use. Openreach is clear that the ONT is not a router and not a traditional modem, and that on its own it does not provide Wi-Fi.

That split matters because:

• Faults can sit in either box. The ONT's lights show whether the fibre signal is arriving, so you can tell which box has the problem.
• The ONT can matter on the very fastest plans. ISPreview reports that EE's 2.3Gbps and 8Gbps "Advanced Full Fibre" plans, launched in July 2026, need an engineer visit to fit one of Openreach's newer 10Gbps-capable ONTs. They are limited to a pilot area (Guildford, Woking and nearby, per ISPreview in July 2026) that ISPreview likens to an open beta. If you're ever offered a plan above 1Gbps, ask whether your ONT needs changing. Our guide to what your home network needs above 1Gbps covers the rest of your kit.

Who owns it

Ownership depends on the network. Openreach says its ONT, PSU and cabling belong to Openreach, not to your provider or to you. Ogi includes the ONT and router in its standard package, and its price guide says the ONT stays in your home unless you ask for it to be removed. Trooli's terms say its ONT modem and router remain Trooli's property.

On Openreach full fibre, an Ethernet cable runs from the ONT's Ethernet port to the router's WAN or internet port. Openreach says the ONT's Ethernet port is sometimes labelled LAN or Data, and Zen's guides also refer to ONTs with a port marked Port/LAN or Port 1. Your router's quick-start guide will show which of its sockets is the WAN port.

You typically need a compatible router for full fibre; Openreach says most providers supply one designed to work with the ONT, and the engineer connects your main device to it and checks it works.

Upgrading from part fibre

If you're moving from part fibre, Zen's upgrade instructions for its FRITZ!Box router say the DSL cable to the phone socket or microfilter is disconnected and an Ethernet cable goes from the router to Port 1 or LAN on the new ONT. Ask your provider whether your current router will be reused. See our guide to upgrading to full fibre.

Using your own router

Ogi says customers can use their own equipment; Trooli's terms allow it "at their own risk". Because the ONT hands over an Ethernet connection, your router needs an Ethernet WAN port, and it may need connection settings from your provider. Our guide to using your own router covers the trade-offs.

Think about this before installation day: Openreach says its ONT should, in almost all cases, stay where it is fitted.

Openreach's checklist asks you to choose a router location in advance. It should be:

• Near a double power socket. (Our note: the ONT's power supply and the router each take a plug.)
• Somewhere suited to Wi-Fi coverage. Openreach says not a dark cupboard under the stairs.
• Close to the ONT. Openreach says the wall-mounted ONT and the router need to be close together.

Openreach gives no maximum distance. Socket needs vary: Gigaclear says it needs two power sockets for its equipment, plus another two if you take its Home Phone service. Airband's installation page says surge protectors protect its equipment from damage from power surges.

A pre-install checklist

1. Pick two or three router spots where Wi-Fi will reach the rooms you use most, and check which has a double socket nearby.
2. Think about wired devices: a router near the TV or desk saves cable runs (see our guide to wiring your home with Ethernet).
3. If you rent, get your landlord's permission for drilling before the visit. Openreach says renters need it.

On the day

Someone over 18 must be there to let the engineer in and agree where the equipment goes. The engineer agrees the cable route and drilling point with you and may ask you to sign a permission-to-work form for digging or drilling. Zen says you can discuss ONT placement with the engineer, subject to technical feasibility, so your planned spot is a starting point, not a guarantee. Openreach's installation checklist says a full-fibre install usually takes around four hours; another Openreach page gives one to four hours, depending on the property.

For the full visit, see our guide on what to expect on full-fibre installation day.

If you want it moved later

Openreach says concerns about where its equipment sits should go to your broadband provider first, and that removing or tampering with the ONT could interrupt your service and could lead to a call-out charge to reinstall it. We couldn't find a published price for moving an ONT inside a home. Ask your provider for the cost in writing before agreeing to a visit, and read our guide to broadband engineer visit charges.

With full fibre, your landline becomes a digital phone service that runs over the broadband. Instead of plugging into the wall socket, the phone usually connects through the router. Openreach says traditional phone lines are going digital on 31 January 2027. GOV.UK adds that most customers are expected to have moved by then, but not all analogue services will be switched off by 2027; your provider will contact you before your line moves.

How you connect a handset depends on the provider:

An ATA (analogue telephone adapter) is a small box that lets an existing analogue phone work on the digital service. In practice, don't count on old phone and extension sockets: plan to keep a handset, or a cordless base station, near the router. Our guide to which phones work on a digital landline has more detail.

Alarms, pendants and other devices

Openreach asks anyone who uses their phone line for an intruder alarm, health pendant or wrist alarm to contact their provider before a full-fibre installation. It adds that CCTV, payment terminals, telecare, door entry and lift phones may also be affected. Our guide to telecare and alarms after the landline switch-off explains what to ask.

GOV.UK says digital landlines can't carry a power connection, so handsets and routers won't work in a power cut without a back-up such as a battery. The ONT needs mains power too, through its PSU.

Ofcom requires providers to offer a solution to customers who depend on their landline. GOV.UK says Ofcom's guidance means at least one hour of emergency access in a power cut, free for those at risk because they depend on their landline. Openreach says providers can supply battery back-up support. Here is what some full-fibre providers publish about their battery units:

• Hyperoptic: the unit should power the Hyperhub and ONT or fibre converter for 1 hour, for a corded phone plugged into the Hyperhub. It is free for customers who depend on the phone service and a paid add-on for others.
• Gigaclear: a battery back-up unit is available on request and should power the router and the internal network termination point for 1 hour.
• WightFibre: an optional battery back-up powers the phone line for up to an hour. See our WightFibre broadband page for packages.
• Airband: a back-up battery is available for vulnerable customers.

So battery units last about an hour, not a day, and on Hyperoptic and Gigaclear's units only a corded phone works. If you rely on the landline in an emergency, keep a corded phone and a charged mobile. Our guide to digital landlines in a power cut covers the options.

The Openreach consumer pages we checked don't explain the ONT lights. Zen, which sells over Openreach, says what a working Openreach ONT shows; Onestream's general ONT help page, not written for one network, explains each light. Check your provider's help pages for your exact box.

Openreach ONT

Trooli ONT

Zen also sells over Trooli's network, so it publishes a Trooli ONT guide; if you're with another provider on Trooli, use it as a reference but follow your provider's fault process. Trooli ONTs come as a black or grey model or a white model, depending on when yours was fitted:

• Power: green.
• Optical: green (the fibre signal).
• Alarm: off.
• Gigabit Ethernet (black or grey model) or 10GE (white model): green or flashing green.

A flashing green Alarm light on a Trooli ONT means a software update is being installed. Zen says to leave it alone; it should take no longer than 15-20 minutes.

For other networks, check your provider's help pages or ask its support team which lights you should see. The lights on your router are a separate set, covered in our guide to what broadband hub lights mean.

Steps 1 and 2 come from Zen's Openreach ONT guide. Step 3 is our own caution.

PON flashing, PON off or LOS red

1. Check for an outage. A flashing PON or red LOS light can mean a wider problem in your area, so look at your provider's service status page or app first.
2. Restart the ONT. Disconnect its power for at least a minute, plug it back in, then wait around 2 minutes for the lights to settle.
3. Ask before resetting. Zen's guide then suggests a reset: holding a pin in the ONT's reset hole for 10-15 seconds. Openreach asks customers to leave the ONT plugged in and switched on and warns that tampering with it could interrupt the service, so we suggest asking your own provider before you reset it.

On a Trooli ONT, Zen's advice for a red or flashing red Alarm or Optical light follows the same pattern: restart, check for outages, then reset.

Power light off

Check the power cable at both ends, the socket switch and any power button on the ONT, then try another socket. If it still won't light, the ONT or power supply may be faulty: call your provider.

Port or LAN light off

Check the Ethernet cable is firmly in at both ends (the router end in the WAN port) and try another cable.

All ONT lights look right, but there's no internet

Then the fibre side is probably fine and, as Zen says, the router settings are the next thing to check. Our guide to connected to Wi-Fi but no internet helps you narrow that down.

Who to call

Your broadband provider, not Openreach. Openreach says concerns about its equipment should go to your broadband provider first,. Note the lights and what you've tried, then see our guide on how to report a broadband fault.

Openreach says plugging an unplugged ONT back in and waiting a few minutes usually restores the connection, but not always, so it is best left plugged in and switched on. Our advice: don't switch it off overnight.

Openreach says that when you switch between providers on its network there is nothing to unplug, remove or return: your new provider uses the same ONT. Plusnet, for example, says an existing full-fibre connection is usually activated remotely in 3 working days. So on Openreach full fibre, comparing broadband providers doesn't mean changing the wall box.

• Moving out: leave the ONT, PSU and cabling where they are. Openreach says the next occupant can often be connected without an engineer visit.
• Moving in: if there's already an ONT, mention it when you order. See our guide to broadband when moving home.
• Switching to a different network: if another network asks you to remove Openreach equipment, Openreach says not to, and to check with your provider first.
• Your router is different. Some providers want it back when you leave; Ogi, for example, says its routers are returned at contract end. See our guide to cancelling broadband.

Altnets set their own equipment rules, so check the terms if you're switching to or from one. Our fibre broadband comparison shows the deals available at your postcode through a partner; it doesn't switch you itself, so you order with the provider you choose.