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Few days ago, my house was connected to fiber optic, which is suppose to provide me with the download speed of 500mb/s.

I am using Windows 10 on my PC that is connected directly to the router, using a new Cat7 cable, and through a Gigabyte TP-Link network adapter, specifically TG-3468 V2.

Problem is, even if the internet says 500mb/s (when tested on sites such as speedtest.net or fast.com) when I try downloading from almost all websites, the download speed is just capped at 1MB/s, and it visibly jumps up and down around the 1MB/S mark. The same thing happens in some programs as well, on VS installer for example, it caps at 3MB/s, on twitch I can't even watch 1080p streams without it buffering non stop. Though downloading from Epic Games or Steam gets the full download speed at all times.

I ran into no problems using this setup in the past (when I had 40mb/s download speed) though I did try other cables (a Cat6 one) and even using the built in adapter on the motherboard. Also it seems like the hardware isn't the issue, since using the same cable on my laptop, or using a different OS, like a linux distro, worked perfectly, with no issue at all.

It's important to mention that all my tests were performed during times that I was the only one using the internet, though I'm not the only connected to it. Nothing is being downloaded in the background for me and the problem hasn't changed so far.

Tried disabling IPV6, tried restarting the router and my PC many times, tried using auto DNS and IP, tried using VPN, tried reinstalling the drivers, and I also tried to boot into Safe Mode with Network, but the problem kept occurring, and the download speed hasn't changed at all.

Any idea on what could it possibly be? And what can I do about it?

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  • Is the Ethernet cable you are using one that was professionally made or was it made by a non-professional? Can you try a different Ethernet cable?
    – David Schwartz
    Commented Apr 15, 2021 at 5:42
  • @DavidSchwartz It's the same one I have used for years without any issues (though I was having 40mb/s). I have no idea how to check if it's professionally made or not, so where can I find a new one?
    – Argaman
    Commented Apr 15, 2021 at 5:55
  • If you don't have another Ethernet cable around, you may want to buy one or borrow one from someone. If the cable is very old, it may be made to standards that are no longer acceptable to modern equipment. For example, the pins-to-pairs mapping may not be correct because older equipment wasn't affected by that.
    – David Schwartz
    Commented Apr 15, 2021 at 5:57
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    We need more information about your hardware, to see if it's capable of such speed (models of computer, disk, router). Try to see if downloading is faster when booting in Safe Mode with Network.
    – harrymc
    Commented Apr 20, 2021 at 19:41
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    I suggest booting from a linux live usb stick and testing then. Judging by your statements it seems this isnt a hardware problem.
    – Silbee
    Commented Apr 23, 2021 at 8:27

1 Answer 1

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The issue could be a bad ethernet cable or that your Network Interface Card is not correctly configured for Gigabit ethernet (or both). It would be helpful to know the age of the computer and operating system and model of NIC- please make sure to post these details when asking questions here.

The first and simplest step is to swap your ethernet cable for another quality Cat6 cable (Cat5e will work, but better to use Cat6). If a single wire or pair is damaged on your current cable you could be getting a marginal Gigabit ethernet connection that is bouncing on and off.

The other steps are to check your NIC. If you have been on 100baseT, 1000baseT is quite different. Older cards often had buggy drivers as well. So make sure you have the latest drivers for your card and then refer to Speedguide.net's network adapter optimization guide - https://www.speedguide.net/articles/network-adapter-optimization-3449. Or better yet, use their TCP Optimizer tool if you are on Windows https://www.speedguide.net/downloads.php. I would pay special attention to your RSS, Receive Window Auto-Tuning, Jumbo Packet and Large Send Offload settings. If your NIC is older it might not be playing well with your router so disabling some of these functions could be the source of the problem.

If not using the TCP Optimizer tool, run these commands from elevated command prompt and reboot and retest after each setting is applied: Turn on the following in order via elevated cmd prompt, reboot and re-test at each step:

netsh int tcp set global autotuninglevel=normal
netsh int tcp set global rss=enabled
netsh int tcp set global rsc=disable
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  • Updated my post to provide more information as you asked
    – Argaman
    Commented Apr 20, 2021 at 18:39
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    Have you been able to verify that you can do a sustained upload and download within your local network? Sounds like your laptop has ethernet (hopefully gigabit) so it would be good to do some large file transfers between the laptop and PC over gigabit through the router to confirm Gigabit ethernet is working correctly on the PC. If that proves ok and the laptop has no speed issues going to the internet, I would look into your router settings to see if you have some QoS services set or some kind of traffic control in place. What router do you have?
    – spaceman-spiff
    Commented Apr 21, 2021 at 4:30
  • Sorry for the delay, I added more information on the post, that insures that this is not an hardware problem at all. but I did try doing somewhat of a large file transfers between the laptop and PC, and it seems like the speed is normal, though I am not sure, since the speed might have slowed down because of the amount of files and their size etc
    – Argaman
    Commented May 2, 2021 at 8:54
  • Run ‘netsh interface tcp show global’ from a CMD prompt and report back your results
    – spaceman-spiff
    Commented May 3, 2021 at 10:00
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    So far, using the tool you provided did solve the issue! Thanks a lot! :) Will give it a couple of days, and will mark as solve if it does stay that way
    – Argaman
    Commented May 4, 2021 at 7:04

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