Crawling Internet Connection

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 -- even for a Notebook computer. When Ethernet is not WORKING, your Mac will drop back to the next working interface, which is usually Wi-Fi).

Hi there Gary Caso,

Create and test with another administrator account to figure out whether the issue is system wide or specific to one account. Here's how: Set up users, guests, and groups on Mac

1. On your Mac, choose Apple menu  > System Preferences, then click Users & Groups .

2. If the lock at the bottom left is locked , click it to unlock the preference pane.

3. Click the Add button  below the list of users.

4. Click the New Account pop-up menu, then choose a type of user.

If you only notice this behavior with one account, test the original account in safe mode. This will start up your Mac so that it performs certain checks and prevents some software from automatically loading or opening, which could help narrow down the cause of issue. How to use safe mode on your Mac.

Best regards.

there is another tweak that may improve speeds slightly more, if you other equipment support it:

setting packet size MTU to larger number than the default 1500, up to about 8,000:

larger than about 8163 requires a change in MacOS using Terminal and a restart.

what is the Internet speed test results?

what speed is your ISP nominally providing?