Fibre Internet Installed But Slow: Fixes That Work

If your fibre internet has been installed but the connection is still slow, the problem is almost never the fibre itself—it is usually your Wi-Fi, router settings, or device. This guide walks through the most common causes and the exact steps to fix them, from simple reboots to changing your DNS settings.

Why Fibre Can Still Feel Slow

Fibre optic internet delivers data as light pulses through glass cables, which is why it can offer symmetrical speeds (same upload and download) and low latency. However, the fibre line usually stops at a wall-mounted ONT (Optical Network Terminal) or a modem. From there, your home network takes over. If your Wi-Fi router is old, poorly placed, or overloaded, it becomes the bottleneck. Also, many people sign up for a plan with high download speeds but don’t realize that upload speed, latency, and Wi-Fi coverage all affect how fast a connection feels.

Step 1: Test Your Speed the Right Way

Before changing anything, get a baseline. Use a wired connection—plug a laptop directly into the router or ONT with an Ethernet cable. Run a speed test (like Ookla or Fast.com) three times at different times of day. Write down the results. Then run the same test on Wi-Fi next to the router and again in the room where you usually work. This tells you whether the problem is your internet service or your home network.

• Wired speed close to your plan: The issue is Wi-Fi.
• Wired speed much lower than your plan: The issue is the router, ONT, or ISP.
• Wi-Fi speed drops in one room: The issue is coverage or interference.

Step 2: Restart Everything in the Right Order

A surprising number of slow fibre issues are fixed by a full power cycle. The order matters because devices need to re-establish a connection cleanly.

1. Unplug the router and the ONT (or modem) from power.
2. Wait at least 60 seconds (this lets capacitors discharge).
3. Plug the ONT back in and wait until its lights show a stable connection (usually 1–2 minutes).
4. Plug the router back in and wait until its Wi-Fi light is steady.
5. Reboot your computer or phone.

This clears the router’s memory and forces it to renegotiate the connection with your ISP. Do this before calling support—it solves more issues than any other single step.

Step 3: Optimize Your Wi-Fi (The #1 Fix)

Wi-Fi is the most common reason fibre feels slow. Here are the specific settings to check and change.

Placement and Interference

Your router should be in a central, elevated location, away from walls, metal objects, microwaves, and cordless phones. If it’s in a cabinet or behind a TV, move it out. Even a few feet can make a big difference.

Use the 5 GHz Band

Most routers broadcast two networks: 2.4 GHz (better range, slower) and 5 GHz (faster, shorter range). Your devices may be stuck on 2.4 GHz. Log into your router’s admin page (usually at 192.168.1.1 or 192.168.0.1) and check the Wi-Fi settings. Make sure the 5 GHz network has a different name (SSID) or that band steering is enabled. Connect your devices to the 5 GHz network for speed.

Change the Wi-Fi Channel

In crowded areas, neighbouring Wi-Fi networks overlap. On the 2.4 GHz band, try channels 1, 6, or 11. On 5 GHz, try a channel in the 36–48 range (lower channels have less interference). Many routers have an “auto” setting that works, but manual selection can help in apartments.

Update Router Firmware

Log into the router admin page and look for a “Firmware Update” or “Administration” section. Manufacturers regularly release updates that fix bugs and improve performance. Install any available update, then reboot the router.

Step 4: Check for Ethernet and Port Issues

If you’re using Ethernet, check the cable. Cat5e or Cat6 cables are fine for gigabit speeds; old Cat5 cables may only support 100 Mbps. Also, make sure the cable is plugged into the correct port on the router. Many routers have one or more gigabit ports and others that are 100 Mbps. If your plan is faster than 100 Mbps, a cable in the wrong port will cap your speed. Check the link speed on your computer: in Windows, go to Network Settings > Ethernet; on Mac, hold Option and click the Wi-Fi icon. It should say 1000 Mbps (or 1 Gbps). If it says 100 Mbps, you have a cable or port problem.

Step 5: Change Your DNS Server

DNS (Domain Name System) translates website names to IP addresses. Your ISP’s DNS server is sometimes slow. Changing to a public DNS server can make web pages load faster, even though it doesn’t increase raw bandwidth. To change it on Windows: Control Panel > Network and Sharing Center > Change adapter settings > right-click your connection > Properties > Internet Protocol Version 4 (TCP/IPv4) > Properties. Choose “Use the following DNS server addresses” and enter 1.1.1.1 (Cloudflare) and 8.8.8.8 (Google). On Mac: System Settings > Network > Wi-Fi > Details > DNS. Add the same addresses. This is safe, free, and reversible.

Step 6: When to Call Your ISP

If you’ve done all the above and your wired speed is still significantly lower than your plan (e.g., you pay for 300 Mbps and get 50 Mbps), the problem is likely on their side. Before calling, have your speed test results ready. Ask them to check the signal level at the ONT. Sometimes the fibre connection itself is faulty, or the ONT needs replacing. Also, check if there are data caps or deprioritization policies—some ISPs slow down heavy users at peak times. If you rent a router from the ISP, ask if it’s capable of your speed tier; older rental routers often aren’t.

Frequently Asked Questions

Why is my fibre slower on Wi-Fi than on Ethernet?

Wi-Fi is a shared, half-duplex medium with more overhead and interference than a wired cable. Even with a “gigabit” router, real-world Wi-Fi speeds are typically 200–500 Mbps, and much less if you’re far from the router or on the 2.4 GHz band. Ethernet will always be faster and more stable.

Does the length of the fibre cable inside my house matter?

No. Fibre optic cable has virtually no signal loss over the distances used in a home (less than 100 meters). The signal loss happens in the connectors and splices, but that’s the ISP’s responsibility. The internal fibre cable length is not a factor.

Can a VPN make my fibre feel slow?

Yes. A VPN encrypts your traffic and routes it through another server, which adds latency and can reduce throughput. If you’re using a VPN, turn it off and re-test. If speeds are fine without it, the VPN server is the bottleneck.

Is it worth buying my own router instead of using the ISP’s?

Often, yes. ISP-provided routers are usually basic models that may not handle high speeds or many devices. A good third-party router with Wi-Fi 6 can improve coverage and throughput. However, make sure you know how to connect it to your ONT—you may need to call your ISP to enable bridge mode or get PPPoE credentials.

Why is my upload speed slower than download?

Most fibre plans are asymmetrical (e.g., 300 Mbps down, 100 Mbps up) unless you specifically choose a symmetrical plan. If your upload is much lower than the plan’s advertised number, test with a wired connection and restart your router. If it’s still low, contact your ISP.

What does “bufferbloat” mean and how do I fix it?

Bufferbloat is when your router buffers too much data, causing high latency and stuttering during heavy uploads or downloads. It makes the connection feel slow even when speeds are fine. Fix it by enabling Quality of Service (QoS) or Smart Queue Management (SQM) in your router settings, which prioritizes real-time traffic like video calls.

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