Ethernet port in Mac studio not working properly

Be sure IPv6 is set to link-local only.

Cabling issues will generally show a hard limit at 100 M bits/sec speeds.

If you can get well above that, you can try adjusting the packet size/MTU to use Jumbo frames. But improvement form this depends on your other equipment being able to handle the larger frames.

on a Mac without making additional buffer size changes, 8,000 size will produce better results, but going over about 8163 will not.

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To run faster than baseband 100 M bits/sec, your ethernet cable must have all eight conductors present and wired correctly.

But 300 M bits/sec suggest you are still using your Wi-Fi connection.

Packets going to the Internet are sent to the TOMOST, WORKING interface in the list at

system preferences > Network

to adjust:

click the Gear Icon below the left panel, and choose "Set Service Order".

Drag Ethernet to the TOP of the list.

(it can stay there -- when Ethernet is not WORKING, you will drop back to the next working interface, which is usually Wi-Fi).

<< a new device that my ISP doesn't recognize >>

if you are connecting through a Router YOU control, your individual devices are NOT visible on the internet to your ISP or anyone else that could possibly see your connection. Only your Router is visible.

Your Router acts as your agent for all Internet transactions, and does Network Address Translation. Only your Router's address is ever sent onto the Internet.

¿what are you getting for internet speed test?

<< Not sure you can get full speed from ethernet with WiFi turned on. >>

yes, you can. They do not interfere with each other. However, as I posted above:

Packets going to the Internet are sent to the TOMOST, WORKING interface in the list at

system preferences > Network

to adjust:

click the Gear Icon below the left panel, and choose "Set Service Order".

Drag Ethernet to the TOP of the list.

(it can stay there -- when Ethernet is not WORKING, you will drop back to the next working interface, which is usually Wi-Fi).

Seeing electricb03 report 300 Mbytes/sec, a common top speed for certain Wi-Fi connections, suggests that their Ethernet is NOT TopMost, so Wi-Fi is being used to reach their Router and the internet beyond.

I am seeing a very strange issue where if I connect ethernet to the Mac studio, over time, it starts to affect my whole network. I massive issues will all google services for about 24 hours. Connected another Mac directly to modem and no issues. Tethering to iPhone no issues. Once I disconnected the Mac studio from ethernet and rebooted switches and access points it was fixed.

Once I connect ethernet to the Mac studio its like a silent count down until the network start breaking. Something is wrong.

some users have discovered that they have a long list of stuff that wants to be sync-ed. To iCloud, photos, one drive, dropbox, back blaze, and similar services. The speed of the Ethernet connection can crowd out other data on your connection to the Internet, causing everything else to slow down.

try this as well:

UN-Check that checkbox

Test a Cat 6a or better Ethernet cable.

What speed are you paying your ISP for?

if higher than 300, you need to contact them.