How to Fix Ethernet Speed Capped at 100 Mbps on Windows

woman in black shirt frustrated at her laptop computer

A durable and reliable Ethernet connection is required to enjoy the full potential of a high-speed fiber broadband, especially for desktop users. But users often find their Ethernet speed capped at 100 Mbps, even on a Gigabit Ethernet. This guide attempts to resolve this strange but common error affecting many Windows users.

Tip: is your Ethernet connection not working? Try these fixes.

1. Ensure Proper Cable Connections

When you connect Ethernet cables to your computer or router, you should notice an audible click or snap once the cable is firmly in place. Sometimes the Ethernet cable is not fully connected, or the “clip/tab” on the cable connector (RJ45 connector) becomes loose or breaks entirely. This can cause the connection between the connector and the computer/router to become less stable.

Router with connected cables.
Image source: Wikimedia Commons

A loosely-connected cable can cause a speed drop for a high-speed 200 Mbps/300 Mbps or faster connection where the network will default to 100 Mbps.

To fix this, disconnect the Ethernet cable from both your router and computer and reconnect it after around 30 seconds. Ensure that the cable is tightly connected at both ends. Even with a broken clip, you can push the cable all the way into the LAN port to eliminate a loose connection as the source of the capped speed.

2. Check Ethernet Cable

If all of your Ethernet connections are in good order, the issue might lie with the cable itself. Ethernet cables are classified according to their data transfer capabilities. Common Ethernet cables used in home and office networks are Cat5, Cat5e, and Cat6. Less commonly used cables are Cat6a, Cat7, and Cat8.

If your home network is using a Cat5 Ethernet cable, your speeds will be limited to a maximum of 100 Mbps, as that’s the data transfer limit of Cat5 cables. Hence, you may just need to replace your cable with a cable that’s at least Cat5e, which is capable of transferring data up to 1000 Mbps.

Ethernet cable view.
Image source: Wikimedia Commons

To identify the type of Ethernet cable you currently have, look at the sheath of the cable. You will be able to find text written on the sheath that will mention whether the cable is Cat5, Cat5e, Cat6, or something else. If you don’t find any text on the cable sheath, it’ll be difficult to identify the cable type, as there are only minor differences in thickness and internal wiring between the different types of cables. For more details, check out the things to know when buying Ethernet cables.

3. Replace RJ45 Connectors

Switching from a lower bandwidth cable like Cat5 to a higher one like Cat5e or Cat6 should ideally fix the issue of capped Ethernet speeds. But if you’re still experiencing intermittent speed drops on your Gigabit connection, it’s possible that the RJ45 connectors at the ends of the Ethernet cable are the culprits.

Often, home setups involve routing the Ethernet cable internally within the walls. This is both for achieving a cleaner look as well as protecting the cable from damage. The default RJ45 connectors that are pre-applied to the cable ends are often too big and need to be removed before routing the cable through the walls. This inevitably requires “re-crimping” or reconnecting new connectors to the cable ends once they come out at the other end.

RJJ45 connector view.
Image source: Wikimedia Commons

It is at this stage that issues will creep up. Either the new RJ45 connector used is incompatible with the cable’s internal wires, or the re-crimping process is wrong. If even one of the internal wires is not connected properly to the connector’s metal contacts, your connection speed will drop to 100 Mbps.

Hence, consider replacing your RJ45 connectors with shielded, high-quality ones. It’s advisable to do this only after you’ve already replaced the cable itself and the issue still persists.

Good to know: these methods may help you fix a slow Wi-Fi connection in your home.

4. Check Ethernet Adapter Settings

If you’ve eliminated the physical sources behind the error, it’s time to move on to the software side of things. Your computer’s Ethernet adapter settings could potentially be limiting your connection speed to 100 Mbps. There are multiple settings here that need to be checked. To ensure your adapter settings are correctly configured, follow the steps below:

  1. Search for and open the Settings app from Windows Search.
  2. Select “Network & Internet” from the options on the left, then “Advanced network settings” on the right pane.
Accessing "Advanced network settings" in Windows.
  1. Click “More network adapter options” under “Related settings.”
Clicking on "More network adapter options" in Windows
  1. In the new window titled “Network Connections,” right-click your Ethernet adapter and click “Properties.” Windows 10 users can click “Change adapter options” after step #2 to open the “Network Connections” window.
Right-clicking Ethernet connection under Network Connections.
  1. In the new Properties window, click the “Configure” button to open additional properties.
Ethernet Properties window with "Configure" button.
  1. Open the “Advanced” tab at the top and select “Speed & Duplex” from the “Property” box.
Choosing value for "Speed & Duplex."
  1. Make sure its value on the right is set to “Auto Negotiation.” This setting will ensure your computer negotiates the maximum speed possible based on your broadband plan and Ethernet cable. Note that you should not choose any other value, such as “1.0 Gbps Full Duplex,” as “Auto Negotiation” is the recommended setting.
  2. Move on to the other settings that could be limiting your Ethernet speed. Ensure that the following settings are set to “Disabled”: “Energy-Efficient Ethernet,” “Gigabit Lite,” “Green Ethernet,” and “Power Saving Mode.”
Choosing value for "Power Saving Mode."
  1. Click “OK” and allow a few seconds for your adapter to reconfigure the new settings. It’ll disable itself and come back online after a few seconds.

5. Update Ethernet Drivers

Configuring the settings in the previous section properly should solve the low-speed issue for most users. But if you’re still unable to fix it, you can try updating your Ethernet adapter drivers. Outdated drivers can often cause a variety of issues, one of which can be capped Ethernet speed.

  1. Right-click the Windows icon and select “Device Manager.”
  2. Under “Network adapters,” right-click the name of your Ethernet adapter and click “Update driver.” Your network adapter will probably have “Realtek,” “Broadcom,” or “Intel” in the name.
Searching for driver updates.
  1. Select “Search automatically for drivers” and let Windows search for the latest network drivers for your adapter.
Ethernet Speed Capped 100 Mbps Device Manager Update Drivers
  1. If available, new drivers will be installed automatically. If not, you’ll see the message: “The best drivers for your device are already installed.”
Drivers already installed window.

Tip: unlock more settings by installing custom firmware on your router.

6. Check Router Settings

Some routers have settings configured in a way that reverts your connection to a “lite or green” mode, where the network speed is capped at 100 Mbps. This can be one of the reasons for the low-speed issue for many users. You can log in to your router’s settings and reconfigure the settings to solve the issue by following the steps below:

  1. Enter “” in a browser window to open your router’s login page. This IP address is a common factory address for consumer routers. Enter “admin” in both the “Username” and “Password” fields and click “Login.” If that doesn’t work, check your router. You should find the username/password information on the back.
Router login window.
  1. Find the settings related to your Ethernet connection. These are likely to be found in menus named similar to “Local Network,” “LAN,” or “Ethernet.” Navigate to that page and find a setting that has “Duplex” in the name. Ensure it is set to “Auto,” “1 Gbps” or “2.5 Gbps.” You’ll see these options based on your network adapter.
LAN information in router page.
  1. It’s also possible that you won’t find any way to manually change the network speed in the router’s settings. In such cases, you can take another look at the other fixes.

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

Frequently Asked Questions

Is a Cat5e cable enough for Gigabit LAN?

A Cat5e Ethernet cable is technically capable of Gigabit speeds, but is inferior to Cat6 cables in terms of grounding and overall cable durability. This is a common source of failure in Cat5e cables that can lead to unstable connections and dropped speeds, even though they are technically certified for up to 1 Gbps speeds. It’s better to go for a higher-grade Cat6 cable to minimize the chances of cable-induced connection issues.

Can 2.4 GHz Wi-Fi support 100 Mbps?

The 2.4 GHz band can technically support speeds of up to 1.2 Gbps on Wi-Fi 6 routers when paired with a fast enough Internet plan. But in practical situations, most people using the 2.4 GHz band likely have Wi-Fi 4 or 802.11n routers, as Wi-Fi 5 only supports the faster 5 GHz band. In these situations, the 2.4 GHz band’s theoretical maximum is around 300 Mbps. But with other factors like interference from other devices and the crowding from other networks on the 2.4 GHz band, actual speeds get decreased even further. In general, you can expect less than half of your plan’s rated speed on the 2.4 Ghz band. Try band steering to get the most out of your 2.4 GHz and 5 GHz bands.

Does Ethernet cable length affect speed?

Yes, Ethernet cables have a rated distance limit beyond which the transfer speeds tend to fall off significantly. For instance, Cat7 cables can transfer up to 100 Gbps, as long as the cable length is within 15 meters or 50 feet. Distance limits for Cat6 or Cat5 are more relaxed and can retain most of their speed until around 100 meters or 300 feet. In practice, you’ll rarely find cable lengths reaching 300 feet in home setups. Therefore, speed reduction due to distance isn’t as much of an issue.

How do I know if my router is Gigabit?

To support Internet speeds of more than 100 Mbps, you need a Gigabit router. Your ISP or Internet Service Provider typically provides a compatible Gigabit router for modern high-speed fiber broadband plans. But if you have an older model you already own and are routing your Internet through that, you may want to check whether your router supports Gigabit. You can check the model of your router printed on its front or back, then check its specifications online.

Image credit: Unsplash. All screenshots by Tanveer Singh.

Tanveer Singh
Tanveer Singh

Tanveer hunts far and wide for PC Hardware, Windows, and Gaming ideas to write about. An MBA in Marketing and the owner of a PC building business, he has written extensively on Technology, Gaming, and Marketing. When not scouring the web, he can be found binging on The Office, running for his life in GTFO, or wrecking karts in Smash Karts.

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