Slow Ethernet Speeds on 2021 MacBook Pro

[ryansebiz]

I have a 2021 16" MacBook Pro and my wife has a 2019 15" MacBook Pro, both running macOS 12.3.1. I have a UniFi gigabit network with a Dream Machine Pro and Switch Lite 16, also running the latest firmware. I ran iperf3 with my hardwired PC as the server and each MacBook Pro as clients one at a time using the same Ethernet cable and Cable Matters USB-C to Ethernet adapter. Here are the results:

• 2019 MacBook Pro: 911 Mbits/sec
• 2021 MacBook Pro: 519 Mbits/sec

I also got the same results with:

• A spare Cable Matters USB-C to Ethernet adapter using the same Ethernet cable
• A Uni USB-C to Ethernet adapter using the same Ethernet cable
• Each of the three adapters with another Ethernet cable
• Each of the three adapters with another Ethernet cable on a different port on my switch
• Repeating the above steps with all three USB-C ports on my 2021 MacBook Pro

UPDATE

Thanks to @lcubed and @glenthompson for solving the problem.

The issue is that macOS does not have the gigabit USB Ethernet drivers to support the Realtek RTL8153 chipset that is used in the USB-C to Ethernet adapters that most brands use (and that I tried).

The solution is to purchase a USB-C to Ethernet adapter with a Realtek RTL8156 chipset because macOS does have the drivers to support these adapters. These are usually 2.5Gbps adapters (not 1Gbps).

I purchased the Plugable 2.5Gbps adapter - https://plugable.com/products/usbc-e2500

Hallelujah gigabit speeds via iPerf3!

 

[glenthompson]

Same version of MacOS? Any differences in other software? Have you tried with a different userid? Can you run the test in safe mode to eliminate any other software as an issue?

 

[ryansebiz]

Same version of MacOS? Any differences in other software? Have you tried with a different userid? Can you run the test in safe mode to eliminate any other software as an issue?

Thanks for your reply. Here are the answers to your questions:

1. Same version of MacOS?
   1. Yes, both Macs are running macOS 12.3.1
2. Any differences in other software?
   1. No
3. Have you tried with a different userid?
   1. Yes, logged into my wife's account on my 2021 MacBook Pro and got the same results
4. Can you run the test in safe mode to eliminate any other software as an issue?
   1. Yes, ran safe mode on my 2021 MacBook Pro and got the same results

Anything else I can try?

Thanks again.

 

[Allyance]

Check your Ethernet "Advance" settings on both machines and see if there is something different between them.

 

[Sheepish-Lord]

Would be curious to see what your wifi results would be as well to narrow it down further.

 

[rehkram]

Something worth testing even if just to eliminate the possibilities:

Have you tried swapping the two machines around and retesting? In other words move your m/c to your wife's physical location, and her m/c to yours, then retesting.

If your speed results are inverted, could be interference, and/or bad cable / keystone RJ45 jack(s) in your location's signal chain.

Are you both plugging-in to wall plate ethernet connecters, or running exposed cables to the switch?

I'm not familiar with iperf3, looks interesting.

 

[glenthompson]

There was something on the most recent ATP podcast that talks about problems with the drivers for different chips. Check out this article for more information. Not sure if it's relevant to your situation.

 

[lcubed]

it may be a realtek chipset issue in the USB-C ethernet adapter

Studio Display & USB-C Ethernet adapter performance issues

@Applefiel do you know how I can check which chipset is in my Anker A7611 USB-A to 1G Ethernet adapter? Note, this particular adapter works absolutely perfect on iOS devices, delivering the full 1G speeds. So, I'm thinking the chipset may be more optimized for iOS and likely to work better with...

forums.macrumors.com

 

[satcomer]

To see the speed of your wires connect while holding 'option' key while clicking the Finder Menu Wi-Fi icon in Finder Menu! A drop-down will give the information of the connection speed is at and frequency and other thing too!

 

[lcubed]

To see the speed of your wires connect while holding 'option' key while clicking the Finder Menu Wi-Fi icon in Finder Menu! A drop-down will give the information of the connection speed is at and frequency and other thing too!

wired or wireless?

the OP is asking about a wired ethernet connection.

 

[satcomer]

wired or wireless?

the OP is asking about a wired ethernet connection.

OK! you made you point! Like others have said an bug in the Ethernet isa if you go into System Preferences->Network, Advanced button and look at the tab to make sure your set to max speed! Plus as former Network Engineer more and more people are still stuck in CAT 5E cables! The cutting edge is 10GH speeds CAT 7 cables! His networking speed would go way up!

 

[ryansebiz]

it may be a realtek chipset issue in the USB-C ethernet adapter

Studio Display & USB-C Ethernet adapter performance issues

@Applefiel do you know how I can check which chipset is in my Anker A7611 USB-A to 1G Ethernet adapter? Note, this particular adapter works absolutely perfect on iOS devices, delivering the full 1G speeds. So, I'm thinking the chipset may be more optimized for iOS and likely to work better with...

forums.macrumors.com

Thank you @lcubed and @glenthompson - this solved the problem. I updated my original post with the solution.