Mac Pro 2019 Ethernet Ports Not Working on Sonoma

EDIT: I started composing and was called away. By the time I was able to finish writing, the new information you added makes the suggestions below redundant in your case.

Readers here appear to have exhausted any more tips and tricks that might be applicable.

The next step is to contact apple support, link below. Be sure you do not let them tell you it is fine if if is not fine. You should get one of the following successful outcomes:

• a solution, including why this happened.

• referral to a Specialist who will call you back and continue to work with you on the problem.

• fling a formal, tracked Bug Report

You can save yourself time and trouble by doing things that would eliminate problems caused by interactions with non-Apple software. (Number one on my list is anything related to VPN. I recommend you remove anything and everything related in any way to any VPN features or software while debugging.)

• Restart in Safe mode, and run that way for a while. ¿Does the problem occur in Safe Mode? if it does NOT, the issue is related to something you added.

• Create a new User account, log in with that Account, and test again. This can eliminate issues caused by settings in one Userid, or caused by damaged settings carried along from older versions of MacOS.

Official Apple Support

<<. My new cables ... are connected to a 5 port switch >>

I suspect the switch is not working properly. a dead port or simply not working.

Self-assigned UP address is the address the port gives itself at power-up. it is typically replaced so quickly with a good local IP address, most users would swear their devices never get a self-assigned IP address. When you are stuck with a self-assigned IP address this is because "no one will talk to me" and give me a good local address.

This typically occurs for Brute force simple physical problems. Broken wires in cables, Switches unplugged, Ports that go completely bad. it is extremely rare for it to be the port on your Mac, and rarer still for BOTH ports to stop working at the same time.

to make connections at speeds over 100 M Bits/ec, you cables must have all eight wires present and wired correctly.

...

<<. I'm guessing there's something up with the latest Sonoma release. >>

I find that extremely doubtful, and there have not been any new issues or more issues than usual reported here.

There ARE some very subtle configuration issue that can cause operating issues, but not getting an IP address is almost always caused by simple Primitive issues.

Have you configured your Mac Ports for autospeed (the default) ?

setting a speed faster than the Switch can handle will result in no connection with no errors messages.

Have you enabled ANY VPN features? These can throw ALL your communications completely offline just by starting to set them up, or turning one low-level feature on.

wait -- I see "VPN and Filers" activated.

check that out, and turn that junk OFF!

in reviewing everything already posted, there some more issues that have not been addressed head-on.

The ports on the Mac Pro 2019, like those on the Mac Studio, are 10G Ethernet capable. that sounds great except for one more footnote: They are NOT Capable of making connections at "only" 100 M Bits/sec speeds, which uses only four of the eight wires and baseband (one bit per signaling interval) signaling.

Making ANY connection requires connected devices support, at MINIMUM, Gigabtit Ethernet speeds, and have all eight wires connected all the way through, because the signal used is modulated (multiple bits per signaling interval , like a modem) and uses far more spectrum which requires more wires.

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The default for 10G Ethernet interfaces may be "energy-efficient". "Energy efficient" drops power to the 10Gb Ethernet chip to save energy.  It is NOT compatible with Fastest Speeds, and could cause issues with auto-speed. For top speeds, In the hardware pane, set Manual, then under Duplex, set: “Full-Duplex, Flow Control” NOT “Full-Duplex, Flow Control, power efficient” to disable power saving and boost top speed.