Router to Modem/PC Auto-Negotiation at 100Mbps (not 1Gbps)

Published by Nyau Wai Hoe - Updated on

In today’s world, where super fast internet is pretty much the standard, having a 1Gbps speed is what most of us expect. But sometimes, you might notice that the speed between your router and modem, or your router and computer, decides to play it slow at just 100Mbps instead of zooming at 1Gbps. This can be a real drag, making everything online slower, from downloads to streaming. It might seem tricky to figure out why this happens, but don’t worry, we’ve got some common reasons and how to fix them.

Also see: Change Ethernet from 100Mbps to 1Gbps in Windows 11/10

Router to Modem or PC Auto-Negotiate at 100Mbps but not 1Gbps

Resolving 100Mbps auto-negotiation cap instead of 1Gbps between router and modem/PC

1. Check and re-seat the Ethernet cable

One big reason your devices might be talking to each other at a leisurely 100Mbps is if the Ethernet cable connecting them isn’t plugged in right or is loose. Here’s how to fix that:

  1. Turn off both your router and the device it’s connected to (could be a modem or your PC).
  2. Unplug the Ethernet cable from both sides.
  3. Have a look at the Ethernet ports on the devices for any dust, debris, or damage.
  4. Plug the Ethernet cable back in securely, listening for a ‘click’ to know it’s in place.
  5. Turn the devices back on and see if the speed’s better.
  6. Try plugging in and out a few times to see if it fixes the negotiation issue.

Replugging LAN cable on Router Modem

If this doesn’t get you to 1Gbps, let’s look at what else you can try.

Linked issue: Ethernet Internet Speed Capped at 100 Mbps (Fix)

2. Try a different Ethernet cable

Another common issue is using a cable that’s not up for the task. Different cables support different speeds:

  • Cat 5: Up to 100Mbps
  • Cat 5e: Up to 1Gbps
  • Cat 6: Up to 10Gbps (but only for short distances)
  • Cat 6a & above: Even faster and longer distances

Auto-Negotiation Cap at 100Mbps

If your cable is old or not the right type, that might be why you’re stuck at 100Mbps.

  1. Disconnect your current cable.
  2. Try a newer or higher category Ethernet cable.
  3. Check the speed again. If it’s faster, your old cable was likely the problem.

But if changing the cable doesn’t help, there might be other reasons for the slowdown.

Related problem: Windows 11 Ethernet “Unidentified Network” (How to Fix)

3. Router configuration issues (auto-negotiation settings)

Sometimes, the settings on your router might not be helping your cause. Here’s how to check:

  1. Log into your router by typing its IP address into a web browser.
  2. Look for “Network” or “LAN/WAN” settings.
  3. Find options like “Link Speed”, “Auto-Negotiation”, or “Connection Speed” and set them to the highest speed (1Gbps or “Auto”).How to set Router Auto-Negotiation setting to 1Gbps instead of 100Mbps
  4. Save the changes and restart your router.

Also, updating your router’s firmware can sometimes solve the issue.

Related resource: Ethernet Not Working in Windows 11 (Fix)

4. Check network card properties

Your computer’s network card settings can also affect your speed. Here’s what to do:

  1. Open the Network Connections Panel on your computer.
  2. Find your Ethernet connection, right-click, and select “Properties”.
  3. Click on “Configure” and go to the “Advanced” tab.
  4. Look for “Speed & Duplex” and make sure it’s set to “1.0 Gbps Full Duplex” or the highest setting available.Windows 11 Set Auto-Negotiation to 1Gbps
  5. Save and restart your computer.

This can help ensure that your computer and router are speaking at top speed.

Other concern: File Transfer Speed Very Slow or Drops to Zero in Windows 11

5. Hardware limitations

Sometimes, the issue is with your devices themselves. If they’re not built for 1Gbps, you won’t hit those speeds.

  1. Check your router/modem specs to see their maximum speeds.Auto-Negotiation 100Mbps Gigabit Router
  2. Look up your computer’s network card model for its speed capabilities.
  3. If they’re not up to par, consider upgrading your hardware.

Remember, your network is only as fast as its slowest component.

Windows 11 Auto-negotiation 1Gbps vs 100Mbps

6. ISP Limitations

Sometimes, the issue might be with your internet service provider (ISP). Here’s how to check:

  1. Double-check the speed plan you have with your ISP.ISP Internet Plan
  2. Use sites like to check your actual internet speeds.Internet Connection Speed Test
  3. If you’re not getting what you should be, talk to your ISP. They might need to update your connection or equipment.

Talking to your ISP can sometimes reveal simple fixes you hadn’t thought of.

7. Factory reset the router (not recommended)

If you’ve tried everything and nothing works, you might consider resetting your router. But be careful, this erases all your settings:

  1. Backup your router settings first.
  2. Understand that you’ll lose all custom settings.
  3. Make sure you have your ISP login details handy.
  4. Press the reset button on your router or use the reset option in the admin interface.Factory reset router
  5. Reconfigure your router from scratch.
  6. Reconnect all your devices.

Only consider a factory reset as a last resort.

Summing up

If you’ve suddenly dropped to 100Mbps after enjoying faster speeds, a bad Ethernet cable is often to blame. If replugging it fixes the issue, even temporarily, get a new cable. But if you’re setting up a new network and run into speed issues right away, the problem might need a bit more digging. Whether it’s hardware, configuration, or your ISP, there are ways to troubleshoot and solve the issue, getting you back to fast internet.

Nyau Wai Hoe
Nyau Wai Hoe is the Founder and Chief Editor of With a degree in software engineering and over 12 years of experience in the tech support industry, Nyau has established himself as an expert in the field, with a primary focus on the Microsoft Windows operating system. As a tech enthusiast, he loves exploring new technologies and leveraging them to solve real-life problems.

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