Mac Mini cannot connect to internet via Ethernet.

[weckart]

I have a Mac Mini M4 connected via ethernet to the main router going via a switch in my room en route. The switch splits the internet between a number of attached devices in the room and allows the devices to talk to each other. Until recently, it had functioned flawlessly. A couple of weeks ago, the Mini stopped connecting to the internet and returned an internal IP number under Networking>Ethernet. I had not installed anything nor changed any settings to prompt this. I have changed ethernet cables and switch ports but that hasn't helped. I now have to connect wirelessly to an AirPort router connected to the same switch. That works, albeit at reduced speeds as I have 1Gb/ps down via ethernet. I know that the switch is not the problem as other devices connected via cable to it still connect to the internet and I can print to a networked printer in my room.

I have gone through all the usual online recommendations to "reset" the network but nothing seems to work. Any other suggestions?

 

[chabig]

Have you rebooted the device that's assigning IP addresses (likely your router)?

Since the Mini is portable, try connecting it directly to the router (no switch) and see what happens. That will narrow the problem–if it works, something is going on with your switch. If it doesn't work, it could be your Mac. (But I doubt it's the Mac).

 

[weckart]

Have you rebooted the device that's assigning IP addresses (likely your router)?

Since the Mini is portable, try connecting it directly to the router (no switch) and see what happens. That will narrow the problem–if it works, something is going on with your switch. If it doesn't work, it could be your Mac. (But I doubt it's the Mac).

Rebooted everything. I can't think the switch is the problem as I am connected to the internet via a router on that switch.

 

[chabig]

I wouldn’t expect the switch to be a problem either. Assuming your TCP/IP settings are good on the Mini (verify DHCP) the most likely problem is the router. Is it serving IP addresses? Do you have a double NAT somewhere?

 

[weckart]

I wouldn’t expect the switch to be a problem either. Assuming your TCP/IP settings are good on the Mini (verify DHCP) the most likely problem is the router. Is it serving IP addresses? Do you have a double NAT somewhere?

Yes. Settings are default. I haven't changed them on the Mini and they served me well until they didn't. The router seems fine and continues to serve IP addresses left right and centre. I can't see a conflict but presumably, the router would just issue another IP number if that happened. I have refreshed DHCP a number of times but I still keep getting a self-assigned address. It's baffling me but, then again, networking is witchcraft at the best of times.

 

[Bigwaff]

I have gone through all the usual online recommendations to "reset" the network but nothing seems to work. Any other suggestions?

Create a new admin user account and log in. Test. If Ethernet work, it software and issue specific to your account. If not work, run Apple Diagnostics.

Use Apple Diagnostics to test your Mac - Apple Support

Apple Diagnostics, formerly known as Apple Hardware Test, can check your Mac for hardware issues.

support.apple.com

 

[tonmischa]

Never mind. Sorry.
Had a thought on manual DNS servers, but I missed the part about the self-assigned IP (probably something like 169.254.x.x ?)

 

[CharlesShaw]

I have refreshed DHCP a number of times but I still keep getting a self-assigned address.

Just a thought. Years ago, while tinkering with security, I drastically narrowed the range of available DCHP addresses, later connected new devices and a newer device grabbed an address an older one had been using. Took me a while to remember what I had done.

 

[weckart]

Create a new admin user account and log in. Test. If Ethernet work, it software and issue specific to your account. If not work, run Apple Diagnostics.

Use Apple Diagnostics to test your Mac - Apple Support

Apple Diagnostics, formerly known as Apple Hardware Test, can check your Mac for hardware issues.

support.apple.com

Tried that but it did nothing. I think that network settings are predetermined before you add new users anyway. When I logged into my new user, WiFi was up and connected already. Apple Diagnostics said everything is dandy. I am stumped.

 

[MarkC426]

A shot in the dark…..
You don’t have WiFi and Ethernet on at the same time do you?

 

[chabig]

I may have missed it. Did you ever try connecting the Mac Mini directly to the router?

And if you never figure this out, just assign the Mini a static IP address in your network’s range. It’ll work.

 

[CharlesShaw]

Do you know of another wired network you'd trust to connect your Mac to? If this were my M4, I'd be thinking about how much of my warranty is left in case it's a hardware failure. Of course if the port were bad out of warranty you could always get a thunderbolt Ethernet adapter, but still.

 

[weckart]

A shot in the dark…..
You don’t have WiFi and Ethernet on at the same time do you?

It's not that.

 

[weckart]

I may have missed it. Did you ever try connecting the Mac Mini directly to the router?

And if you never figure this out, just assign the Mini a static IP address in your network’s range. It’ll work.

Yeah. That's going to be my next step. I'm all out of other ideas.

 

[weckart]

Do you know of another wired network you'd trust to connect your Mac to? If this were my M4, I'd be thinking about how much of my warranty is left in case it's a hardware failure. Of course if the port were bad out of warranty you could always get a thunderbolt Ethernet adapter, but still.

I'm in the UK so I have about 5 years left if it is a hardware issue.

 

[Fishrrman]

Chabig has the answer.

Why do you keep putting off a direct connection between the mini and the router?
This eliminates the switch altogether, taking that "out of the chain".

Move the Mini if you must, but do this before you do anything else.

If the ethernet starts working again with a direct connection, next I would try:
Unplug all other devices connected to the switch.
Is there any way to do a factory reset on the switch? If so, DO IT. Then...
Move the switch to where the router/Mini is.
Re-establish the connection there.
Does the problem disappear, or does it come back?

If nothing you try seems to work, I'd try this:
(I ALWAYS do things the hard way)
1. BACK UP the contents of the Mini if you don't already do that now. I'd recommend using SuperDuper to an SSD (hard drive might work if you have a spare)
2. Use "the nuclear option" on the Mini -- the "erase all content and settings" option in System settings. This should restore the Mini to "moment zero" -- the moment you first pressed the power-on button after you took it out of the box.
3. Restore your data from the backup using setup assistant
4. Try the ethernet again.

 

[weckart]

Why do you keep putting off a direct connection between the mini and the router?
This eliminates the switch altogether, taking that "out of the chain".

Because it is already pretty much established that the switch is not the problem. I put the Mini into recovery mode to eliminate any rogue settings as being responsible. I also connected it directly to the router and... nothing. It looks pretty much like a hardware fault atm, so I shall have to take a trip to the Apple store. This is only the second computer of very many I have owned that has had a broken ethernet. The other was the Apple Powermac MDD. That one was so fubar that I could not even get a PCI ethernet card to work in it.

Thanks everyone for your suggestions.