Ethernet speed wont go above 100mbs while port speed is set to 2.5gbs (full duplex)

Question

Ethernet speed wont go above 100mbs while port speed is set to 2.5gbs (full duplex)

Kevin Hill 20

Hi all!. The problem is I recently upgraded my internet speed to 1gbs but after doing speed tests, cant get speed to go above 100mbs on my Win11; on both wifi and hard line. Have older Optiplex system that runs 980mbs down on hard line and 460mbs via wifi. Used same hard line and same wifi channel so I know its not the router, switch, or cable. Adjusted port settings from auto nego to full duplex. Adjusted jumbo frames from minimum 1514 to maximum 90XX. Added throttle speed lines to registry. Nothing changes. Yes, all updates on software and drivers are done. I'm at a loss on what else to do/check. Open to ideas and help. Thanks!Fun11 - Ethernet port settings.jpg

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Answer accepted by question author

EmilyS726 265.1K Independent Advisor

Hello

I don't think I can straight up give you the solution, but I hope you don't mind me reviewing a few things first.

Can you launch powershell, and run this command:

Get-NetAdapter | Select Name, Status, LinkSpeed

Then share a screenshot of the result please.

Next, Please type cmd in the search on the taskbar. Don't press enter key yet. Instead, choose "run as administrator" to launch Command Prompt. Then run this command

netsh interface tcp show global

Share another screenshot please. Thanks!!

Kevin Hill 20 Reputation points

2026-08-25T20:54:42.1166667+00:00

Thanks for the reply. Here are the results of those commands:
EmilyS726 265.1K Reputation points Independent Advisor

2026-08-25T20:59:54.43+00:00
Thanks.

So this is not a 100 Mbps Ethernet negotiation problem. The cable, NIC, and switch port are successfully establishing a 2.5 Gbps link.

Can you run cmd in admin mode again, this time, run this command:

netsh int tcp set global autotuninglevel=normal

Then run this command again and verify that "Receive Window Auto-Tuning Level : normal"

netsh interface tcp show global

Then restart the computer. Run a speed test and let me know if anything changes.
EmilyS726 265.1K Reputation points Independent Advisor

2026-08-26T17:38:03.6633333+00:00
Can you run this command again and show the screenshot?

netsh interface tcp show global
Kevin Hill 20 Reputation points

2026-08-26T18:37:46.85+00:00

results and speed test.jpgof course. here are the outputs. nada changed...
EmilyS726 265.1K Reputation points Independent Advisor

2026-08-26T18:45:24.04+00:00
This didn't change though. Did you run this command?

netsh int tcp set global autotuninglevel=normal
Kevin Hill 20 Reputation points

2026-08-26T21:24:02.2666667+00:00

yep.... looks like changing that value did the trick!! you are a genius! Many thanks!
EmilyS726 265.1K Reputation points Independent Advisor

2026-08-26T21:26:40.76+00:00

Awesome. I am glad to hear.

If all is good, feel free to mark the answer for this thread, or let me know if you need anything else from me.
Kevin Hill 20 Reputation points

2026-08-26T21:30:19.6133333+00:00

nah, its all good now. just need to know how I can sponsor your next Starbucks run...
EmilyS726 265.1K Reputation points Independent Advisor

2026-08-26T21:33:09.17+00:00

Lol. That's very kind.

Since I got a "didn't resolve vote" from yesterday, it would help a lot if you would consider clicking on the "accept answer" to mark the answer for this thread. Appreciate it!

2 additional answers

Your answer

Kevin Hill 20 Reputation points

2026-08-25T20:54:42.1166667+00:00

Thanks for the reply. Here are the results of those commands:
EmilyS726 265.1K Reputation points Independent Advisor

2026-08-25T20:59:54.43+00:00

Thanks.

So this is not a 100 Mbps Ethernet negotiation problem. The cable, NIC, and switch port are successfully establishing a 2.5 Gbps link.

Can you run cmd in admin mode again, this time, run this command:

netsh int tcp set global autotuninglevel=normal

Then run this command again and verify that "Receive Window Auto-Tuning Level : normal"

netsh interface tcp show global

Then restart the computer. Run a speed test and let me know if anything changes.
EmilyS726 265.1K Reputation points Independent Advisor

2026-08-26T17:38:03.6633333+00:00

Can you run this command again and show the screenshot?

netsh interface tcp show global
Kevin Hill 20 Reputation points

2026-08-26T18:37:46.85+00:00

results and speed test.jpgof course. here are the outputs. nada changed...
EmilyS726 265.1K Reputation points Independent Advisor

2026-08-26T18:45:24.04+00:00

This didn't change though. Did you run this command?

netsh int tcp set global autotuninglevel=normal
Kevin Hill 20 Reputation points

2026-08-26T21:24:02.2666667+00:00

yep.... looks like changing that value did the trick!! you are a genius! Many thanks!
EmilyS726 265.1K Reputation points Independent Advisor

2026-08-26T21:26:40.76+00:00

Awesome. I am glad to hear.

If all is good, feel free to mark the answer for this thread, or let me know if you need anything else from me.
Kevin Hill 20 Reputation points

2026-08-26T21:30:19.6133333+00:00

nah, its all good now. just need to know how I can sponsor your next Starbucks run...
EmilyS726 265.1K Reputation points Independent Advisor

2026-08-26T21:33:09.17+00:00

Lol. That's very kind.

Since I got a "didn't resolve vote" from yesterday, it would help a lot if you would consider clicking on the "accept answer" to mark the answer for this thread. Appreciate it!

Answer 1

Horace Wiggins 530

Look at the Control Panel and your Ethernet Connection. What does that show? What is the make and model of the router you have? When you do a speed test what do you get?

Example image of my Ethernet adapter.

Example image of User's image

Kevin Hill 20 Reputation points

2026-08-25T21:32:58.07+00:00

Thanks for the reply but sadly its not my router, switch, or cables. If it was, the other computer connected to the same equipment would be just as limited on speed; its not. I've even swapped the cat6 cable between the two computers and the results were the same. The problem is isolated to the PC and not the supportive gear. But here is the image you asked for. Hopefully you can see something I'm missing.
EmilyS726 265.1K Reputation points Independent Advisor

2026-08-25T21:35:42.7066667+00:00

Kevin, I don't think it is router/cable issue either.

Did you have a chance to change the autotunninglevel item from my last reply. I am waiting to hear how that goes.
Kevin Hill 20 Reputation points

2026-08-26T17:36:29.6733333+00:00

hi again! Yeah I went ahead and put the speed/duplex control back to autonego and rebooted. didnt help.

Answer 2

Bulldog 4,465

As an FYI: Your port speed and your internet speed are separate, unrelated things. Your port speed measures the bandwidth your hardware is capable of handling. Your internet speed comes from your Internet Service Provider.

Your port speed is something you consider if, for example, you share large files with other devices on your network.

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