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Which UNI-D Port Should I Use on My NBN Box?

If you’ve got NBN Fibre to the Premises (FTTP) at your home or business, you’ve probably seen the box on your wall with several ports labelled UNI-D 1, UNI-D 2, UNI-D 3, and UNI-D 4. But which UNI-D port are you meant to use?

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What is a UNI-D Port?

A UNI-D port (User Network Interface – Data) is one of the ports on your NBN connection box (also called an NTD or Network Termination Device). These ports are where your internet service provider (ISP) connects your internet service.

If you’re on FTTP, you’ll typically see four yellow UNI-D ports on the box. But here’s the catch:

Only one port is usually active—the one assigned by your provider.

 

UNI-D Port 1 vs Port 2 (or 3 and 4)

  • Port 1 is the most commonly used port. Most providers will activate your internet on UNI-D 1 by default.
  • Port 2, 3, or 4 may be used if:
    • You’re switching providers and your new ISP uses a different port.
    • You have multiple services (e.g. business internet + home internet).
    • You’re using a failover or backup connection.

Important: Don’t just plug your router into any port. It must match the port your ISP has provisioned.

 

So… Which UNI-D Port Should You Use?

To find out:

  1. Check your welcome email or setup guide – your ISP usually tells you which port is active.
  2. Try Port 1 first – it’s the default in most cases.
  3. Still not working? – Contact your provider and ask:
  4. “Which UNI-D port is my service active on?”

 

Can You Use More Than One UNI-D Port?

Yes, technically, each port can support a separate service. Here are some examples:

  • A family running business internet on Port 1 and home internet on Port 2.
  • Using Port 3 for a backup provider in case your main internet goes down.

But unless you’ve arranged this setup with your providers, only one port will usually be active.

What Happens to UNI-D Ports When You Switch Providers?

When you switch NBN providers, the new service is usually provisioned on a different UNI-D port—often the next available one.

For example:

  • If your original provider was using UNI-D 1, your new provider may activate the service on UNI-D 2.

  • This avoids service disruption while the old connection is still active during the transition period.

What does this mean for you?

  • Your modem/router must be plugged into the correct, newly activated port.

  • If you connect to the old port by mistake, you won’t get internet access—even if the lights are on.

🛠 Tip: Always check with your new provider to confirm which UNI-D port they’ve activated, especially after a switch.

 

 

Troubleshooting Tips

If your NBN isn’t working, check:

  • You’ve connected your modem/router to the correct UNI-D port.
  • The lights on the port are blinking, showing active data flow.
  • You’re using the WAN port on your router (not a LAN port).

Still unsure? That’s where we come in.

 

Central Telecoms Can Help

Not sure which UNI-D port to use? We’ll check it for you—no jargon, no stress.

Whether you’re setting up a new service or switching providers, we’ll make sure your router’s plugged into the right port, and your internet is good to go.

Need help connecting your NBN Fibre?

Contact us today and we’ll guide you step-by-step.

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