Sonoma: Ethernet (Internet) Speed resets to about 100 Mbps after restart

[clingfreeze]

I ran into this strange behaviour with Sonoma (all Betas and the official version) that is bugging me. I have a glass fiber connection with 500 Mbps up / 500 Mbps down speed, Zyxel AX7501-B0 router. When I cold boot up my Mac mini M2 Pro, the Ethernet speed (Internet speed) resets to about 100 Mbps. Also happens if I just restart the Mac. I have to disconnect the Ethernet cable from the Mac and reconnect the cable to the Mac, and voilà, the speed I get is 500 up / 500 down.

I have no idea why this happens, and how to test what could be the culprit. Maybe one of you cool cats have an idea. This did not happen with Ventura.

 

[vanc]

You can check your network hardware status. Usually, you should have 1000baseT for the speed. If you only get 100baseT, you would be limited to 100Mbps.

Just go to "System Settings" and "Network" and click on the network device for your fibre connection and click on details button on the top right, then "Hardware" on the bottom left.

 

[clingfreeze]

Thanks vanc! I checked the settings, they were 1000BaseT and full duplex.

I then switched "Configure" from "Automatically" to "Manually", and then back to "Automatically".

Did a restart, and got 500/500.

Shut down the Mac, and then did a cold boot. Got 500/500.

That seemed to fix the settings. At least I hope so.

I'll report back if the problem still persists the next days.

Once again, thanks for the help.

 

[clingfreeze]

It's strange, after some time, when set to "Automatically", it resets back to 100BaseT. I have now set it to "Manually" and 1000BaseT. I hope this works.

 

[vanc]

The physical layer negotiation is usually done by firmware. Not sure if Sonoma somehow updated the NIC controller's firmware. Manual setting should be fine as your router should have no problems with full duplex 1000baseT.

 

[clingfreeze]

So far the problem seems to be solved with manually setting the hardware status to 1000baseT. Thanks again, vanc!

 

[smithrh]

I've had an extremely similar issue, in the end it wound up to be a bad Ethernet cable, so don't forget to check that as well.

The connection randomly negotiated down to 100 and remained there. The cable was good enough to have a solid 100mbps connection but not 1gbps.

Replaced the cable and it's been fine since.

 

[clingfreeze]

Yes, the cable was a concern, too. So I exchanged it, but the behaviour was the same.