How to Fix Ethernet Speed Capped at 100 Mbps on Windows - Make Tech Easier

To fully utilize the capabilities of high-speed fiber broadband through a stable Ethernet connection, especially for desktop users, it's crucial to address the common issue of Ethernet speeds being limited to 100 Mbps despite having a Gigabit Ethernet setup. This guide aims to help Windows users troubleshoot and resolve this frustrating yet widespread problem.

Tip: If your Ethernet connection is not functioning, consider these troubleshooting steps.

Table of Contents

• 1. Verify Cable Connections
• 2. Inspect the Ethernet Cable
• 3. Upgrade RJ45 Connectors
• 4. Adjust Ethernet Adapter Settings
• 5. Update Ethernet Drivers
• 6. Review Router Settings
• Frequently Asked Questions

1. Verify Cable Connections

Ensure that Ethernet cables are securely connected to both your computer and router, indicated by a distinct click or snap sound upon insertion. A loose connection or a damaged "clip/tab" on the RJ45 connector can result in an unstable connection, leading to reduced speeds.

A loosely connected cable can downgrade high-speed connections above 200 Mbps/300 Mbps to 100 Mbps. To remedy this, disconnect the cable from both ends, wait about 30 seconds, and reconnect it firmly. Even with a broken clip, ensure the cable is fully inserted into the LAN port to avoid speed limitations due to loose connections.

Did you know? If you're using an Ethernet switch, hub, or splitter, understanding their roles can be beneficial.

2. Inspect the Ethernet Cable

If connections appear secure, the cable itself might be the issue. Ethernet cables vary by their data transfer capabilities, with common home and office types being Cat5, Cat5e, and Cat6, and less common ones like Cat6a, Cat7, and Cat8.

Using a Cat5 cable caps your speed at 100 Mbps. Upgrading to at least a Cat5e cable, capable of 1000 Mbps, could solve the problem.

Identify your cable type by checking the text on the cable's sheath. Without this, distinguishing between types can be challenging due to minor differences. For more insight, review the considerations when purchasing Ethernet cables.

3. Upgrade RJ45 Connectors

Switching to a higher bandwidth cable like Cat5e or Cat6 might resolve speed issues. However, if you still experience intermittent speed drops, the RJ45 connectors may be at fault.

In setups where cables are routed through walls, the original RJ45 connectors might be replaced, which can lead to issues if not done correctly. Improper connection of internal wires to the new connector's metal contacts can limit speeds to 100 Mbps.

Consider replacing your RJ45 connectors with high-quality, shielded ones, especially if the problem persists after changing the cable.

Useful to know: Similar techniques might improve your home Wi-Fi connection speed.

4. Adjust Ethernet Adapter Settings

If physical issues are ruled out, look into your computer's Ethernet adapter settings, which might be capping your speed at 100 Mbps. Here’s how to check and adjust these settings:

1. Open the Settings app via Windows Search.
2. Navigate to “Network & Internet,” then to “Advanced network settings.”

3. Click “More network adapter options” under “Related settings.”

4. Right-click your Ethernet adapter in the “Network Connections” window and select “Properties.” Windows 10 users should click “Change adapter options” post step #2.

5. Click “Configure” in the Properties window to access additional settings.

6. Go to the “Advanced” tab and select “Speed & Duplex.”

7. Set it to “Auto Negotiation” to allow your computer to maximize speed based on your plan and cable. Avoid other settings like “1.0 Gbps Full Duplex.”
8. Disable settings that could limit speed, such as “Energy-Efficient Ethernet,” “Gigabit Lite,” “Green Ethernet,” and “Power Saving Mode.”

9. Click “OK” to apply the changes and allow the adapter to reconfigure.

10. Update Ethernet Drivers

Properly setting the adapter settings should resolve speed issues for most. If not, updating your Ethernet adapter drivers might help, as outdated drivers can cause various connectivity problems.

1. Open “Device Manager” by right-clicking the Windows icon.
2. Right-click your Ethernet adapter under “Network adapters” and select “Update driver.”

3. Choose “Search automatically for drivers” to let Windows find and install the latest drivers.

4. If new drivers are found, they will be installed; otherwise, you'll be informed that the best drivers are already installed.

Tip: Enhance your router's capabilities with custom firmware for more settings.

6. Review Router Settings

Some routers might have settings that limit connections to “lite or green” modes, capping speeds at 100 Mbps. To adjust these settings:

1. Access your router’s settings by entering “192.168.1.1” in a browser and logging in with “admin” credentials or router-specific details.

2. Find and adjust Ethernet-related settings under “Local Network,” “LAN,” or “Ethernet” to “Auto,” “1 Gbps,” or “2.5 Gbps” based on your adapter's capabilities.

3. If manual speed adjustments are unavailable, revisit the other troubleshooting steps.

Good to know: Understand the difference between “Access Point” and “Repeater” modes on your router.

Frequently Asked Questions

Is a Cat5e cable sufficient for Gigabit LAN?

While a Cat5e cable can technically handle Gigabit speeds, it's less durable and more prone to issues than Cat6 cables. Cat5e might lead to unstable connections and speed drops, so opting for Cat6 is advisable for better reliability.

Can 2.4 GHz Wi-Fi support 100 Mbps?

The 2.4 GHz band can theoretically reach up to 1.2 Gbps with Wi-Fi 6 routers, but most users with Wi-Fi 4 or 802.11n routers on this band can expect a maximum of 300 Mbps. Real-world speeds are often lower due to interference and network congestion. Consider using band steering to optimize your Wi-Fi performance.

Does Ethernet cable length affect speed?

Yes, Ethernet cables have distance limits beyond which speeds decrease. For example, Cat7 cables maintain 100 Gbps up to 15 meters, while Cat6 and Cat5 retain most of their speed up to 100 meters. Home setups rarely exceed these lengths, so distance-related speed drops are less common.

How do I know if my router is Gigabit?

For Internet speeds over 100 Mbps, a Gigabit router is necessary. Your ISP usually provides one with high-speed plans, but if using an older model, check its model number and online specifications to confirm Gigabit support.

Image credit: Unsplash. All screenshots by Tanveer Singh.

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