Optus Modem Lights Meaning – What Each Light Means (& How to Fix)
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Not sure what your Optus modem lights are telling you? Here’s exactly what the Internet, 4G Backup and Telephone lights mean – and what to do when they’re red or off. If it won’t come online, The Original PC Doctor can get you connected, onsite or remotely, no fix no fee.
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Optus modem lights – what each one means
On the Optus Ultra WiFi (Gen 2) and similar Sagemcom modems, the front lights tell you your connection status:
| Light | Meaning | What to do |
|---|---|---|
| Internet solid blue | Online via fixed NBN | All good |
| Internet blue + 4G Backup green | Running on 4G backup | Fixed line is down – check NBN box/cables |
| Internet off + 4G Backup red | No internet, backup not working | Restart; check SIM; if it persists, diagnose the line |
| Telephone solid green | Home phone connected | Normal |
| No lights | No power | Check power switch and socket |
Most common: no internet light or red 4G backup
If the Internet light is off and the 4G Backup is red, the NBN is down and backup isn’t working – power-cycle the modem (off 30 seconds, on), wait a few minutes, and recheck. If it doesn’t recover, we diagnose whether it’s the NBN line, the modem or the settings and get you back online.
Common Optus modem problems we fix
- Internet light off
- 4G Backup light red
- Phone light not green
- Lights won’t settle after an outage
- Flashing that won’t stop
- Not sure what a colour means
On Optus modems the Internet and 4G Backup lights together tell the story — a blue internet light is good, while a red 4G backup with no internet means both the fixed line and the backup need attention.
Why The Original PC Doctor
- Since 2001 — 24+ years of Australian computer & network support
- No fix, no fee — you only pay if we solve it
- Onsite & remote — whichever is faster, same-day available
- All NBN types — FTTP, FTTN, FTTC, HFC, plus 4G/5G backup
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Frequently asked questions
What does a red light on my Optus modem mean?
A red 4G Backup light with the Internet light off means there’s no internet and the 4G backup isn’t working. Power-cycle the modem and check the SIM; if it persists, the line or modem needs diagnosis.
What colour should the Optus modem light be?
The Internet light should be solid blue – that means you’re online via the fixed NBN connection.
What does a blue light mean on the Optus modem?
Solid blue on the Internet light means you’re connected via the fixed NBN. If the 4G Backup light is green too, you’re on 4G backup because the fixed line is down.
My Optus modem has no internet light – how do I fix it?
Power-cycle the modem (off 30 seconds, back on) and wait a few minutes. If the Internet light stays off, we diagnose whether it’s the NBN line, the modem or settings and get you back online.
More Optus modem guides
← Back to the Optus Modem Setup & Support hub.
Optus Ultra WiFi (Gen 2) setup · Optus 5G Home Internet modem setup · Optus modem login & password
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