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What happens to your phones when the nbn drops out

Every provider quotes four nines. Only some of them have an answer for the afternoon the fibre gets dug up.

Published 7 min read Updated
The claim
Almost everyone quotes 99.99% platform uptime
The gap
Platform uptime isn’t your uptime
What matters
Automatic failover to mobile, configured in advance
Test it
Unplug the router and ring your own number

Every cloud phone provider quotes an uptime figure and the figure is almost always 99.99%. It’s usually true. It’s also answering a question nobody asked.

Platform uptime measures the provider's infrastructure: servers in a data centre with redundant power, multiple upstream carriers and staff who get paged at 3am. That equipment is genuinely very reliable.

The thing that fails isn’t that. The thing that fails is the fibre in the street outside your office, cut by a contractor who wasn’t looking at the plans.

The question to ask instead

Not "what is your uptime". Ask: at the moment my site loses internet, what physically happens to the next inbound call, and how long does it take to happen?

There are three answers in the market and they’re very different.

Answer one: voicemail

The platform notices your handsets are unreachable and does the default thing, which is to send callers to voicemail. Technically correct. Commercially, a day of lost enquiries.

Answer two: a manual divert

Somebody logs into a portal from their phone and redirects the main number to a mobile. This works, and it depends entirely on somebody noticing quickly, knowing the password and having signal. In practice it happens about forty minutes in.

Answer three: automatic failover

The platform detects the loss of registration and immediately routes inbound calls direct to nominated mobile numbers. The call flow, the queue order and the after-hours rules still apply. Callers notice nothing. Staff answer on their mobiles until the fibre is fixed.

Only the third answer is worth anything, and it’s the one that has to be configured before the outage, not during it.

The other half: call quality

Outages are dramatic and rare. Quality problems are undramatic and constant, and they cost more over a year.

Voice traffic doesn’t need much bandwidth. A call uses roughly 100 kilobits per second in each direction. What it needs is consistency: low jitter, low packet loss, and priority over the video call somebody is having in the next room. A 100/40 nbn service with no quality of service configured will deliver worse calls than a 50/20 service with it.

Three things fix most of it:

  • Prioritise voice on the router. Ten minutes of configuration, enormous difference. Any provider that sells you the connection as well should do this by default.
  • Cable the handsets. Wi-Fi is fine for a laptop and mediocre for a phone that can’t tolerate a 200 millisecond gap.
  • Watch the upload. Most nbn plans are asymmetric and most call quality complaints are an upload problem, usually a cloud backup running at 2pm.

Why bundled providers have an edge here

When one company sells you the phone system and the internet, there’s nobody to hand the problem to. They can see the connection, they configured the router, and they can’t claim the fault is with the other vendor because there’s no other vendor.

Both Australian platforms in our comparison sell nbn alongside voice and both do automatic outage failover to mobile. Telstra and Optus will sell you the connection too. The other six, Dialpad, Aircall, Zoom Phone, 8x8, GoTo Connect and Microsoft Teams Phone, sell software only, which means the internet, the router and the argument about whose fault it’s all remain yours.

Test it before you need it

On a quiet afternoon, unplug the router and ring your own main number from a mobile. What happens next is your actual uptime. Everything else is a slide.

The two that topped our 2026 scorecard

Uniden Voice over Cloud scored 95/100 at $34.90 per user per month with calls, AI agents and 40+ call-flow features included. VOCPhone scored 92/100 and is the one to shortlist if the phone is a sales tool.

Questions

Does 99.99% uptime mean my phones will always work?

No. That figure describes the provider platform, which sits in a data centre with redundant power and multiple carriers. It says nothing about the internet connection between that platform and your office, which is the part that actually fails.

What is the best outage protection for a small business?

Automatic failover that routes inbound calls direct to nominated mobiles when the platform loses contact with your site. It costs nothing extra on the better platforms, takes ten minutes to configure, and is the difference between a quiet afternoon and a day of missed calls.

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