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nbn box lights: what each one actually means
Every light on your nbn connection box, by connection type, taken from nbn's own published tables rather than from one provider's version of them. Pick your technology and read the table, or work backwards from a light that is worrying you.
Last reviewed: 15 August 2026 · by Alien IT Solutions
First, which one do you have?
The lights on your box mean different things depending on which nbn technology your address is on. This is the reason the guides you find are so confusing: each one is written about a single technology, or a single provider's hardware, and none of them say so at the top.
If you do not know which you have, the shape of the box is the quickest tell. A box with a row of lights labelled Power, Optical and Alarm is fibre to the premises. Four lights reading Power, Downstream, Upstream and Online is HFC. A small unit whose lights are blue rather than green is fibre to the curb. And if you have no nbn box at all, only a modem from your provider, you are on fibre to the node or fibre to the building.
Pick your connection type
The three things worth knowing before you read any light
- Watch for a full minute before you decide. nbn's own fixed wireless guide asks you to watch the indicators for about 60 seconds and check they are not changing or resetting. Lights that cycle mean something different from lights sitting in the wrong state, and almost nobody looks long enough to tell them apart.
- Flashing is not automatically bad. On several of these boxes a flashing light means a firmware update is running, and switching the box off partway through an update is genuinely worse than the problem you started with.
- Write down the colour and the behaviour of every light before you call. Steady or blinking, and which colour. That is the first thing you will be asked, and having it ready is the difference between a fault being raised and a call ending in a restart suggestion.
Or work backwards from the light that is worrying you
If one particular light sent you looking, start there instead. Each of these collects that state across every technology that documents it, so you can compare what it means on your box against what it means on someone else's.
- There is a red light on my nbn boxA red light means something different on each nbn technology. What red means on FTTP, FTTC, HFC and fixed wireless, and what to do about each.
- My nbn box has no lights at allNo lights on your nbn connection box usually means power, not network. What to check, in order, and when it is the box itself.
- The lights on my nbn box are flashingFlashing is often normal on an nbn box, and sometimes it means a firmware update you must not interrupt. Which is which, by connection type.
Before you touch anything
- Do not go up a ladder or onto a roof. That includes fixed wireless antennas and dishes. nbn's own fixed wireless guide tells you to contact your provider rather than touch an outdoor unit mounted more than 2 metres off the ground. There is nothing you can fix up there that is worth a fall.
- Do not open the nbn connection box, and do not touch the pit or the lead-in cable. That equipment belongs to nbn, not to you or your provider. Fibre terminations carry laser light that you cannot see and should not look into. Opening it can also end your service and leave you liable for the repair.
- Leave the backup battery alone beyond what your provider's own script tells you. If you have the optional Power Supply with Battery Backup, follow your provider's instructions for it and nothing more.
- Burning smell, scorch marks, or a modem too hot to touch: stop. Switch it off at the wall, unplug it, and do not plug it back in. Tell your provider it needs replacing. There is no troubleshooting step that comes before this.
Where this comes from
Every light state and every figure on this page comes from the sources below, each checked on 15 August 2026. Where a provider's guide disagrees with nbn's, the provider is describing their own hardware and you should follow theirs.
While you are on the phone to them anyway
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