Windows Capped At 100Mbps Internet Speeds (Here’s 9 Fixes I Tried)

I’ve had a REALLY annoying bug on my Windows workstation PC in recent months: its internet speeds randomly drop from Gigabit speeds, to just 100 Mbps download and upload speeds. When this happens, my actual network link speed is capped at this low 100 Mbps rate too – so this isn’t some random ISP glitch.

I tried various solutions over the past 9 months and I think (or hope?!) that I’ve finally fixed it. I literally tested everything, from swapping network switches and Ethernet cables to changing loads of Windows settings. Soin this videoI run through everything you should try too.

If you prefer text over video, please read on for the guide/transcript version of this video.

Video Transcript And Guide

Hey everyone, one of the first things I did after moving house last year was ensure that I had Gigabit networking EVERYWHERE. This is partly due to nerdy pride on my part, but it’s also because I have lots of large video files – and anything below Gigabit speeds is just way too slow. However I’ve been having an annoying issue for the past 9 months: this PC’s network speeds suddenly become REALLY slow. They’re capped at just 100 Megabits per second.

This might not SOUND too bad, but when you’re moving 20 Gigabyte files around, it is pretty frustrating. Thankfully though I THINK that I’ve finally fixed it so here’s everything I tried, and what you should try too if you’re getting bad Ethernet speeds on Windows 10 or 11 – and spoiler alert, this isn’t PURELY a hardware issue, it can actually be a bug within Windows too.

Turn It Off And On Again!

So the FIRST thing you should try is to turn it off and back on again. Yes I know that’s an annoying tip, but sometimes I rebooted my PC ormy network switch(or both) and then the network speeds went back up to 1 Gigabit. Removing the Ethernet cable, and putting it straight back in again, also sometimes helped. So that’s good, but unfortunately it often reverted back to 100 Meg speeds after a few hours or days. It certainly wasn’t a permanent fix, meaning that something else is going wrong along the “network chain”. And that’s the difficult thing about this problem – you’re likely to have MANY “hops” between your ISP’s modem and your actual PC. In my case I have an Eero router, then a network switch, then another network switch and finally my desktop PC.

There’s also multiple Ethernet cables here too, along with RJ45 wall jacks that I plug my Ethernet cables into. If ANY of these have a fault, I could be capped to 100 Meg speeds – so tracking down the exact cause of this problem can be difficult because it’s not exactly practical to go out and buy a new Eero Router or £100s worth of new network cable. That’s why turning things off and on again can help, because if the problem is with a single router or cable, it can help you isolate this fault.

Windows Network Settings

But if that doesn’t work, the SECOND thing I’d probably check is the network settings within Windows. Whether you connect to your internet with an Ethernet cable or over WiFi, you should check what the link speed is. This is what speed your computer’s network is running at. To check this, click the network icon in the bottom right tray, select your network and click the “i” icon. This will open a network properties box and you should scroll down until you see the “Link Speed” option. This is the speed your computer has “negotiated” with your router ornetwork switch. So if this is below the speeds that you were expecting, then the problem MIGHT be due to a Windows issue. Of course, it can also be due to a bad cable or a few other “hardware” problems which I’ll discuss in a minute, but let’s look at the Windows settings first.

Search for “View network connections” and right click on the active network (basically the one you’re connected to) – this will probably be “Ethernet” if you’re using a network cable, or “WiFi” if you connect to a wireless router. Click “Properties”, “Configure” then “Advanced”. If you’re on Ethernet, scroll down to “Speed & Duplex” and ensure that “Auto Negotiation” is selected. If it says “100 Mbps” for example, then that’s why your speeds are being automatically capped down. The Auto option is best here because this will at least give your PC a CHANCE to connect at Gigabit, 2 and a half Gig or10 Gigabit speeds.

However if youinstead use Wi-Fi, you’ll probably want the two channel widths to be set to “Auto” and ensure that “Fat Channel Intolerant” is Disabled. You might also want to decrease the Roaming Aggressiveness to Lowest or Medium Low because Medium can sometimes cause issues. Finally move to the Power Management tab at the top, and ensure that the power saving option is UNTICKED – otherwise this might be causing problems. You should then restart your computer and see whether the problem is resolved.

Bad Ethernet Cable?

That takes care of the BASIC network settings within Windows, and while there ARE some other parts of Windows that might be causing issues, I wanted to discuss the next most likely cause which is (three) a bad Ethernet cable. In order to get Gigabit speeds, all of the Ethernet cables should be in good working order, and they should be at least CAT 5e or upwards – simple CAT5 cable is not sufficient.

If you connect over WiFi you might be thinking “well this doesn’t apply to me”, but it’s likely that there’s at least one Ethernet cable in your home – for example connecting the ISP’s supply to your router. In my case there’s actually 5 Ethernet cables: one from my modem to myEero router, then another from my router to a network switch. The switch then connects to a wall patch and so there’s a fourth cable running inside my walls, to get to my study. I then plug a fifth Ethernet cable in atmy study, to connect to my PC. If ANY of those cables are damaged in any way, I IMMEDIATELY get 100 Megabit speeds. That’s because Ethernet “CAT” cables have 8 wires inside of them, and to achieve Gigabit speeds, every single wire must be unbroken and terminated correctly at the plug end. So if a chair rolled over an Ethernet cable and damaged a SINGLE wire, I get 100 Meg speeds.One time I actually purchased a CAT5E cable in a shop, but it wasn’t terminated correctly – only 4 of the 8 wires were connected in the end.

This meant that the cable was never able to achieve the Gigabit speeds that it advertised. In terms of how to fix this, you can either get an Ethernet Tester which can show you whether any of the wires are badly terminal. Or you could just try swapping out each cable one at a time, and see whether the link speed goes back up to Gigabit.

Check Your RJ45 Patches

That brings me onto the fourth potential issue here, and it’s a bad RJ45 wall patch. This is the “wall socket” that you plug your Ethernet cable into and this is what it looks like behind it. While it’s rare for these to fail, one of the 8 terminal connections could be loose – and this will again result in Gigabit speeds. So if you’re able to, it could be worth gently pulling these out to rule out any loose connections.

Router Or Switch

The fifth cause of slower than expected connection speeds is your switch or router – ESPECIALLY if you’ve ever changed the settings within the management panel. Sometimes your router allows you to limit the bandwidth of a particular device, and you might have done this years ago and forgot about it – so it’s worth double checking the settings. Equally enabling settings likeQoS and parental controlcan also have an impact too, so it might be worth restoring some of the default values and seeing whether that helps. If not, in rare cases the switch or router itself could be faulty. Everything fails, after all, and a bad Ethernet port could certainly limit your computer’s connection speeds. So if you’re using Ethernet, try moving the cable to a different port on the switch.

Equally you could try plugging your computer directly into your ISP’s modem and see whether the problem persists. If connection speeds go back to Gigabit after this, then you might have a bad switch or router.

Driver Updates

HOWEVER if your connection speeds are still low even when plugged directly into the ISP’s device, you’re probably experiencing a bug within Windows. I like Windows 11 overall, but I swear that I have more networking bugs compared to previous versions. So the sixth thing I would try is to ensure that the network card’s drivers are updated. To do this, open “Device Manager” and expand out “Network Adapters”. If you connect over WiFi, you’ll probably see an entry that says “Intel Wireless” or similar. If you use Ethernet, you’ll probably see words like “Realtek”, “PCIe” or “GBe” – something like that. Right click on that entry, and select Update Driver:

If you’re able to, I would also try updating the motherboard’s BIOS. Sometimes these are handled through Windows Updates (especially if you have a main-brand laptop), but if you have a custom build desktop, for example, it’s likely that you’ll need to follow yourmotherboard’s BIOS updatesteps.

Virtualization On Windows

The seventh cause here is an annoying one. One day I enabled Hyper-V, or I downloaded VirtualBox, I can’t remember which. BUT I started getting 100 Meg speeds AFTER installing virtualization.

So I dug into things a bit, and I noticed that my PC had a bunch of extra network interfaces added within the “Network Connections” section of Windows. That’s fairly normal for virtualization of course, but Windows was randomly “connecting” to these networks – and that’s when I had the slower network speeds. Then it switched back to the normal network, and it went back to Gigabit speeds – which was odd. So I ended up disabling Windows virtualization features and this helped a lot. But obviously if you REALLY need to run VMs then you’ll probably need to do some extra debugging, however there certainly does seem to be some annoying interplay between recent Windows versions and virtualization – at least in my case.

Device Association Root Enumerator?!

So I had replaced my faulty Ethernet cables AND disabled virtualization, and all was well in the world, right? Well it was, for many months. But a few weeks ago, my PC started getting 100 Megabit speeds AGAIN. As a result, I threw my PC out the window and bought a new one. Kidding. I did some MORE digging and I found a weird entry within Device Manager that was related to my HP Printer.

Some people online said that this device can cause networking clashes and so I disabled it, and I immediately went back to Gigabit link speeds. Woohoo! I don’t really know why this entry appeared, nor why it nuked my network speeds, but disabling it definitely worked for me:

As a general suggestion, if you suspect that a Windows bug might be causing your networking issues, boot into “safe mode with networking” and see what link speeds you get there. If everything looks fine in safe mode, then one of the installed programs or drivers is the culprit, and you may need to reinstall or reconfigure it.

Change The NIC

If you’re still having issues though, the ninth option is to look at replacing the device you’re using to connect to the internet. It might be that your computer has a separate WiFi card in it, and so replacing that card with a new one might help fix the issue. Or if you were relying on your motherboard’s built-inEthernet or WiFi, buying a separate card – like this 10 Gig PCIe card – can also help.

I now FINALLY have a home network that I’m proud of, and I no longer experience these annoying speed drops which is a relief. I show offmy home networkin another video if you wanted to check that out, and I hope you found these tips useful.

Tristan has been interested in computer hardware and software since he was 10 years old. He has built loads of computers over the years, along with installing, modifying and writing software (he’s a backend software developer ‘by trade’).Tristan also has an academic background in technology (in Math and Computer Science), so he enjoys drilling into the deeper aspects of technology.Tristan is also an avid PC gamer, with FFX and Rocket League being his favorite games.