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What do the NBN connection box lights mean?

The lights on your NBN modem have different meanings based on their presence, colour and flashing. Here’s how to interpret them.

By Nathan Lawrence

Jun 26, 2024

6 min read

To get online with the NBN, you need some key ingredients. The first is an NBN plan from an NBN provider. Next, you generally need an NBN-provided modem, which is sometimes called a connection box (or just “NBN box”) or network termination device (NTD). Then you either need an NBN-compatible router or modem-router to connect your home to the internet.

The thing is, with all of those pieces in place, you may still not get online. Some of the answers to why you’re not online can be gleaned from the lights on your NBN box. Particular light states—flashing, solid or off—and colours have different meanings, and we’re here to translate those for you.

Before we get into all of that, though, here’s a look at popular NBN plans today.

Different NBN connection boxes

While NBN modem, connection box and NTD are terms that are used interchangeably, they refer to different devices that get homes online based on the specific technology connecting those abodes. Confusing, right? Let’s simplify it. If you don’t know which NBN technology connects your home, head to the NBN Co website, enter your address, then make note of the technology listed under the ‘Technology used in your connection’ results page. It’ll be one of the following (ranked in order of best to worst):

FTTP NBN connection box lights

If your home is connected to the NBN via FTTP, your NBN modem has several lights with different meanings:

Power
Optical
Alarm
UNI-D1
UNI-D2
UNI-D3
UNI-D4
UNI-V 1/2
Update

Here’s how to translate the NBN connection box lights for the power indicator, and recommended actions (where applicable):

Off (no power): Check the power is connected and turned on. Still no light? Call your NBN provider.
Red (backup power): If you have a batter backup, it kicks in during a mains power failure (for up to five hours).
Solid green (normal): The NBN modem is working as it should.
Flashing green (start-up): The FTTP modem is powering on or restarting (it’ll turn solid green once complete).

NBN modem optical indicator lights:

Off (externally disabled): Contact your NBN provider for more information.
Red (connection lost): Contact your NBN provider about a potential outage.
Solid green (normal): The NBN modem is working as it should.
Flashing green (normal): As above.

Alarm indicator lights:

Off (no connected devices): Connect a router or modem-router to your NBN modem.
Red (faulty box): Contact your NBN provider for assistance.
Green (normal): The NBN modem is operating as it should.

Data indicator lights (UNI-D1 through 4):

Off (no active service): This could mean your router or modem-router is off, but if that device is on, contact your NBN provider for assistance.
Solid orange (1Gbps Ethernet connection): The NBN modem is operating as it should at 1Gbps speeds.
Flashing orange (1Gbps Ethernet connection): As above.
Solid green (10 or 100Mbps Ethernet connection): The NBN modem is operating at 10Mbps or 100Mbps speeds (dependent on your router or modem-router).
Flashing green (10 or 100Mbps Ethernet connection): As above.

Voice indicator lights (UNI-V):

Off (no active phone service): Contact your NBN provider if you’d like a phone service.
Solid green (phone in use): NBN modem is working as it should.
Flashing green (phone off hook): Your phone has been in use or off the hook for more than an hour.

Update indicator lights:

Off (normal): NBN modem is working as it should.
Red (software failure): Contact your NBN provider and say your NBN connection box has failed to download an update.
Green (software downloading): No action required.

FTTP is able to connect to any NBN speed tier, so here’s a list of popular NBN 1000 plans from our comparison engine.

HFC NBN connection box lights

HFC NBN modems have lights for power, downstream, upstream and online. The power indicator light will be off when there’s no power, but will be on with a solid green during start-up and normal functionality. It’s a similar story for the downstream indicator light, except it will flash during the NBN modem’s power-on self-test and downstream-search phases.

The only difference between the downstream indicator light and the upstream indicator light is the latter will flash during the power-on self-test, then disappear during the downstream search, before returning to a flashing state during the upstream search phase. Finally, the online indicator will be off when there’s no power as well as during the downstream and upstream search phases, before flashing during the final step of powering on and then solid green when it’s ready to connect.

When all lights are solid green, everything is working as it should. If your HFC modem has flashing lights for upstream and downstream while the online indicator is off, it means you’re not connected to the NBN. Wait a couple of minutes, then power off the HFC modem and check the coaxial cable is firmly attached. Power the modem back on and contact your NBN provider if it doesn’t work. If you notice the downstream and upstream lights flashing, that means the HFC modem is downloading a firmware update. Don’t power it off; it should go back to solid green once the update is finished.

Like FTTP, HFC homes can connect to every NBN speed tier. Here’s a daily updating list of popular NBN 250 plans from our database.

FTTC NBN connection box lights

Homes connected to the NBN via FTTC technology have an NTD that has four indicator lights: power, connection, DSL and local area network (LAN).

Here’s how to translate the power indicator lights:

Off (device off): Plug in your FTTC modem and turn it on.
Blue (power on): Normal operation.

Connection indicator lights:

Off (no NBN connection): Check all cables are correctly connected.
Flashing blue (start-up): Wait up to 20 minutes for setup to complete.
Solid blue (NBN connection): Normal operation.
Solid or flashing red (potential external issue): Contact your NBN provider for assistance.
Alternating between red and blue (line fault): Disconnect incompatible devices from telephone wall sockets. If it persists, contact your NBN provider.

DSL indicator lights:

Off (broadband down): Contact your NBN provider if the power and connection lights are solid blue (also check the DSL cable is firmly connected on both ends).
Solid blue (DSL synchronised): Normal operation.
Flashing blue (DSL sync or update): Wait for the light to turn solid blue.

LAN indicator lights:

Off (no Ethernet connection): Check your Ethernet connection between the NBN modem and router or modem-router.
Solid or flashing blue/amber (data flowing): Normal operation.

FTTC homes can connect to every NBN speed tier up to NBN 100. Check out this list of popular NBN 100 plans.

FTTB and FTTN NBN modem-router lights

Of the NBN technologies, FTTB and FTTN homes are the most straightforward to get online, requiring only a single modem-router device instead of a modem and a router for every other NBN technology. The catch is modem-routers aren’t typically provided by NBN Co. NBN providers like Telstra, Vodafone and Optus include NBN modem-routers with their plans. These other NBN providers below offer the option to purchase a modem-router separately:

Here’s a look at popular picks from these providers today if you’re in an FTTB or FTTN home and on the lookout for a new NBN plan.

As for modem-router lights, well, it depends on the networking device you’re using because there are dozens of options from a range of manufacturers. In general, look for light configurations that are similar to FTTC. Specifically, the power, internet and DSL lights should be on, and a LAN-activity light should either be solid or flashing to indicate a functional connection. For specific modem-router light translations, consult your user manual or reach out to the device provider.

Fixed Wireless NBN connection box lights

Homes with Fixed Wireless NBN have a connection box that uses power, status, outdoor unit and signal indicator lights. Here’s how to make sense of the Fixed Wireless NBN modem power indicator lights:

Off (no power): Check that the NBN modem power cable is properly connected and turned on.
Green (powered on): Normal functionality.

Status indicator lights:

Flashing green (internet activity): Normal functionality.
Solid green (device test mode): Wait until the NBN modem testing completes.
Flashing amber (start-up and installation): Wait until the NBN modem starts up or completes installation.
Red (system fault): Contact your NBN provider for help.

Outdoor unit indicator lights:

Solid green (online): Normal functionality.
Flashing green (internet activity): Normal functionality.
Solid red (offline): Contact your NBN provider for help.
Flashing red (error): Contact your NBN provider for help.

Signal indicator light:

Red (low signal): Normal functionality.
Amber (medium signal): Normal functionality.
Red (high signal): Normal functionality.

If you live in a Fixed Wireless home, here’s a list of popular Fixed Wireless plans.

NBN Sky Muster satellite connection box lights

Unlike the other NBN modem options above, the Sky Muster satellite NBN NTD only has a single status light. Here’s what the different NBN modem lights mean:

Off (no power): Check the power cables and turn on the NBN modem.
Solid white (powering up): Wait for the NBN modem to fully power on.
Pulsing white (attempted network entry): As above.
Solid blue (online): Normal functionality.
Pulsing blue (busy device): Normal functionality.
Solid amber (sleep mode): Use the internet on a device to wake up the NBN modem.
Pulsing amber (installation mode): Wait for the NBN modem to finish installation.
Solid red (device error): Power off your NBN modem, wait 60 seconds, then power it back on. If the problem persists, contact your NBN provider.
Pulsing red (fault): Contact your NBN provider for help.

Live in a home connected to the NBN via Sky Muster satellite? Here’s a list of popular satellite NBN plans.

Router and WiFi mesh lights

While the specific light colours, indicator names and symbols may vary between different router and mesh WiFi models, there are some consistent ideas that can help guide interpretation. Generally, blue, green or white lights are positive and red indicates a problem. Solid lights are better than flashing, but flashing lights are common during networking device start-up and may persist to indicate local network activity for specific lights (i.e. LAN, WiFi and USB). Lights for Ethernet ports will not power on at all if they aren’t connected to a device. There may also be lights for WiFi and USB. If in doubt, consult the device documentation or reach out to the device manufacturer to explain the different router light meanings.

NBN modem lights frequently asked questions

What do the lights on my NBN modem mean?

The lights on your NBN modem indicate regular activity or potential issues. You generally want solid or flashing blue lights to indicate solid internet activity.

How many lights should be on my NBN modem?

Depending on your NBN modem, you generally want to see lights for power, downstream, upstream and potentially a flashing light for activity (when connected to an external router or modem-router).

What do lights on my modem mean?

Consult your modem documentation for specific light translations but, generally, blue, white or green lights are used to indicate power, connectivity and internet activity. Red lights may indicate an issue.

Written by

Nathan Lawrence

Nathan Lawrence has been banging out passionate tech and gaming words for more than 11 years. These days, you can find his work on outlets like IGN, STACK, Fandom, Red Bull and AusGamers. Nathan adores PC gaming and the proof of his first-person-shooter prowess is at the top of a Battlefield V scoreboard.