NBN Slow-Speed Troubleshooting: Why You're Not Getting Your Plan Speed

People blame the NBN first, but real-world speed is a ‘weakest link’ problem across the entire chain: ISP → connection type → NBN box → router → cabling → WiFi band → your device. Pay for 1000M and any one bad link can leave you at 100M or less. A real case: a student in Eastgardens on a 1000M Telstra plan was getting ~20M downloads — after we corrected the router configuration and ran a wired test straight into the router, it hit ~1000M. We then ran an Ethernet line from the living-room router to the bedroom PC for a rock-solid connection. The plan was never the problem.

A random Speedtest over WiFi proves nothing. Do it right:

• Wire it: connect a computer to the router/box by Ethernet — don't test only over WiFi (especially 2.4GHz, which is easily interfered).
• Average it: test a few times, at different times of day, and take the average.
• Compare to your plan: a 100M plan should land near 90–100M; a 250M/1000M plan should reach at least ~80% of the label.
• Note the time: only slow at 7–10pm usually means ISP peak-hour congestion, not a home fault.

You can run a test on our speed-test tool. For a quick 5-step self-check, see the FAQ My internet is slow — how do I diagnose it?

The most common home-side bottlenecks, and the fixes:

• Old router: a decade-old unit may cap at 100M or choke on many devices. A 1000M plan needs a gigabit-class router.
• Old cabling: Cat5 caps at 100M — use Cat5e or Cat6 minimum. A single bad/old cable in the path drops the whole link.
• Old network card: some laptops only have a 100M port or old WiFi; check the spec if a wired test is still low.
• Fix: gigabit router + Cat6 cable + a device that can actually accept the speed.

Buying replacements? See Buying a router & gear.

Even with a fast line, WiFi can be the ceiling:

• Band: 2.4GHz is slow and crowded — connect to 5GHz (or WiFi 6) for real speed. 2.4GHz is only for range/old devices.
• Placement: a router stuffed in a corner, cupboard or behind a TV loses a lot. Put it central, high, and out in the open.
• Coverage: thick walls or a two-storey home may need mesh rather than one router.
• Prove it: if a wired test hits your plan but WiFi doesn't, the line is fine — it's a WiFi problem to solve with band, placement or mesh.

If your speed is fine most of the day but tanks every evening (roughly 7–10pm), that's classic peak-hour congestion — too many people on your ISP's capacity at once. It's not a fault in your home and rebooting won't fix it. Consistent, nightly slowdowns are a sign to consider a more reliable provider (see choosing a provider). Occasional evening dips are normal on any network.

Speedtest shows 200M but Bilibili loads like dial-up? That's not your NBN — it's the international link between Australia and China. Local content is fine; cross-border traffic is the bottleneck, because the data physically travels much further and shares congested international routes. Home fixes won't change that physics. If only China-bound traffic is slow while everything Australian is fast, stop blaming your router — high-quality access to China content needs a dedicated path (you know the kind).

If it feels like nobody gives you a straight answer, that's because a home network is a classic complex system: many links in series, invisible signals (WiFi interference, band congestion, neighbours' routers, walls, microwaves), and behaviour that changes by time, room and device. Symptoms are often intermittent and won't reproduce on demand — fast in the day, slow at night; fine on your phone, slow on the laptop; smooth in one room, dropping in another. That's exactly why a methodical, tool-assisted diagnosis beats guesswork, and why we always test wired-first and isolate one variable at a time.