High Speed Motherboard Ethernet on Desktop Machine Disappears from Hardware caused by Electric wires creating field interference

My ethernet was working and then stopped working.
I can't even connect to my router but if I turn on wifi that works fine.
For a little while the light was not on on the router (when it broke) where the ethernet was plugged in but then it showed as connected but still did not work and now 8 hours later as I made this post it went back to saying ethernet wire not connected. The light on the router has gone dark again but it had been on all day while I was trying to find the issue.
I tried different ports on the router
I even tried static IP just in case dhcp was the issue on the router.
I hoping this is simple and I'm missing something and so are claude and gemini that gave me lots of suggestions and non worked.

I uninstalled the Realtek driver and replaced it with generic from windows, still not working.
Changing the speed to 100Mbps full duplex, did nothing
reset ethernet / all those things.
Plugged a different computer into the ethernet cable and works fine.
The ipconfig /renew - just takes a long time and then says timed out

• MSI PRO X870E, Realtek 5GbE onboard NIC
• Actiontec 1900a modem/router
• Windows 11
• Was working, stopped suddenly during HDR color profile setup
• WiFi works fine on same machine
• Static IP set manually still can't ping router
• ipconfig /renew times out
• SFC found nothing
• Multiple driver installs including Windows default
• BIOS LAN toggle tried
• All standard network resets done
• DHCP Client running, Network Location Awareness now running
• No third party security software
• No ghost adapters in Device Manager
• on motherboard bios I have off internal graphics card

The suggestions that did not help include the above and:
netsh winsock reset
netsh int ip reset
netsh int ipv4 reset
netsh int ipv6 reset
ipconfig /flushdns
ipconfig /release
ipconfig /renew
ipconfig /registerdns
sfc /scannow
make sure to disable wake on lan or energy efficient ethernet
Did the bios settings->advanced->integrated and disable onboard lan - reboot and then change it back to enable and try again.
We tried turning off windows firewall
The latest AMD drivers are installed - AMD Chipset Drivers Revision Number 8.05.04.516

I just switched back from default driver to the Realtek PCIe 5GbE Family Controller
and changed the settings as claude recommended.
Go to Device Manager → adapter → Properties → Advanced tab and do all of these, then test:

• Energy Efficient Ethernet → Disabled
• Green Ethernet → Disabled
• Gigabit Lite (if present) → Disabled
• Speed & Duplex → force it. Try 1.0 Gbps Full Duplex first; if no luck, drop to 100 Mbps Full Duplex purely as a diagnostic
• Jumbo Frame → Disabled
• Flow Control → Disabled
• VLAN ID (if present) → 0 / disabled — a stray VLAN tag would make the router silently drop every frame
  
  Now it no longer says cable not connected but still not working.
  ipconfig /renew says:
  An error occurred while renewing interface Ethernet : unable to contact your DHCP server. Request has timed out.
  The static IP does not work anyway - hope this all helps to know what the issue is.

clearing CMOS fixed it after a recent BIOS update, with the NIC link flapping beforehand.

 

Going to test linux on the usb drive and if it works, the hardware is cleared as good.


I turned on the WIFI and when I see the 10.10.0.73 in the arp -a after doing the arp -d. That is the address that should be assigned to the ethernet as I have it stored in the router as reserved and assigned to the ethernet physical address.

Why did it get added back to the arp table right after delete when the ethernet adapter still does not know that is its address.

C:\Windows\System32>ipconfig

Windows IP Configuration


Wireless LAN adapter Wi-Fi 2:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :

Wireless LAN adapter Wi-Fi 3:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :

Wireless LAN adapter Wi-Fi 5:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :

Wireless LAN adapter Wi-Fi:

Connection-specific DNS Suffix . : Home
Link-local IPv6 Address . . . . . : fe80::e7ef:88e3:c0d0:bb1d%20
IPv4 Address. . . . . . . . . . . : 10.10.0.85
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 10.10.0.1

Ethernet adapter Ethernet:

Connection-specific DNS Suffix . :
Link-local IPv6 Address . . . . . : fe80::1e78:796c:932a:4d0e%5
Autoconfiguration IPv4 Address. . : 169.254.182.2
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . :

Ethernet adapter Bluetooth Network Connection:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :

C:\Windows\System32>arp -d

C:\Windows\System32>arp -a

Interface: 169.254.182.2 --- 0x5
Internet Address Physical Address Type
224.0.0.22 01-00-5e-00-00-16 static

Interface: 10.10.0.85 --- 0x14
Internet Address Physical Address Type
10.10.0.69 20-df-b9-b3-df-24 dynamic
10.10.0.73 28-d0-43-e9-fe-e6 dynamic
224.0.0.22 01-00-5e-00-00-16 static


Yes, agreed — if Linux gets an IP on ethernet immediately, the hardware is definitively ruled out and this is purely a Windows problem.


And yes, both addresses were self-assigned defaults:

• 169.254.x.x is Windows self-assigning an IPv4 address when DHCP fails — called APIPA
• fe80::x is the IPv6 equivalent — a link-local address that self-configures automatically

Neither means real connectivity. They're both Windows saying "I gave up waiting for proper network configuration."


One thing that output confirms though — back to that ARP finding:


The ethernet adapter has a link-local IPv6 address gone now, but earlier it had one. That self-configured IPv6 address required actual frame exchange with the router to generate. So frames WERE crossing the wire. The router WAS responding at Layer 2.


But IPv4 DHCP requests are getting no response. That asymmetry — Layer 2 works, IPv4 doesn't — still points to something specifically intercepting or dropping IPv4 traffic on that Windows interface.

 

I tried running Linux off of USB and it also could not connect to the network.
So, it was either hardware failure or something at the BIOS level and not part of windows.
Sometimes it would not connect and othertimes it would say onboard NIC intermittently reports cable unplugged, link light on the router comes and goes.
clearing CMOS fixed it after a recent BIOS update, with the NIC link flapping beforehand.
I had not done a clearing of CMOS after the BIOS update - clearing CMOS resolves a corrupted initialization state that a firmware update occasionally leaves behind, and doing it after a BIOS update is a good habit that can prevent this.
It had worked for a few days after the BIOS update and then I had the issue.
I will try several reboots and shutdowns to see it keeps working.
I will then update my settings on the BIOS and see if it breaks, if you don't hear back from me it means it did not break again.

 Fixed - The real fix.

The big question was why was it happening and the final answer was ... drum role please ....

The Ethernet wire in the attic went over 3 electrical wires that created a large disruptive magnetic field.
I just moved the wire to go around that spot and then come down into the computer closet and all the problems went away.

Otherwise the Ethernet wire was not running for long distances along with electric wires.
I also replaced my old wall Ethernet jack that had 8 screw style from 2003 with the new connector but that did not fix the problem but might have been its own problem if not addressed.
In short, the laptop could handle the magnetic interference but the desktop with it's 5GB speed shuts down and requires the hardware full drain for it to come back.
Not a easy problem to track down and all the AI help was going down the wrong paths.
Only obvious and easy once you know this is the issue and then AI will say, oh yeah, that is the issue.