Ethernet connection stopped working with Windows 7

[#1]

Try ipconfig as @Dan_the_Van explained.

Check the IP4 Address is within the local network range.

Check Subnet Mask is 255.255.255.0

Check Default Gateway is the IP address of you router

[#2]

@Anonymous Just to confirm that the motherboard network port light does indeed stay lit amber after changing from green when Windows starts.

I tried rebooting the router, but no luck there.

Later, when I have more time, I guess I need to go into the router control settings and look into the things you mentioned, which will be new to me.

[#3]

@Champnet, IPCONFIG /ALL is only showing
Host Name (my selected PC name)
Primary DNS suffix (blank)
Node Type (Hybrid)
IP Routing Enabled (No)
WINS Proxy Enabled (No)

[#4]

Try ipconfig on it’s own.

Details should be under ethernet something or other.

[#5]

Looking at your details posted earlier you're seeing Windows IP Configuration

You're not seeing Ethernet adapter Ethernet, Wireless LAN adapter Wi-FI or the various Wireless Local Area Connection.

Have a look in Control Panel-->Network & Sharing Center-->Change adapter settings you should see Ethernet & Wi-Fi Card details. If not run Device Manager-->Network adapters if the devices are not there click action-->Scan for hardware changes

[#6]

@Champnet In message 8 above I mentioned that there are just 2 Network Adapters listed in Device Manager: “Realtek PCIe GBE Family Controller” and “TAP-Windows Adapter v9”, but now I can see from Control Panel\Network and Internet\Network Connections that neither of those relate to the broadband Ethernet connection. That’s because Control Panel lists a 3rd item, specifically as a Broadband Connection: “WAN Miniport (PPPOE)”, which it shows with status “Disconnected”.

When I highlight that and click “Start this connection”, on the submenu above, it launches a pop up window prompting for User Name and Password, which default to blank. As I didn’t think such parameters are needed for the Plusnet connection I left them blank and hit Connect (in the pop up window). It then attempted to connect via the WAN Miniport, but failed with Error 651: “The modem (or other connecting device) has reported an error.”

The Ethernet port on the motherboard remained lit amber the whole time.

[#7]

@Champnet I did also try the “Scan for hardware changes” in Device Manager, but that failed to add to the 2 Network Adapters listed - ie. Device Manager still doesn’t show the WAN Miniport (PPPOE) connection.

[#8]

In message 8 above I mentioned that there are just 2 Network Adapters listed in Device Manager: “Realtek PCIe GBE Family Controller” and “TAP-Windows Adapter v9”, but now I can see from Control Panel\Network and Internet\Network Connections that neither of those relate to the broadband Ethernet connection. That’s because Control Panel lists a 3rd item, specifically as a Broadband Connection: “WAN Miniport (PPPOE)”, which it shows with status “Disconnected”

@Colpeper1944 

Realtek PCIe GBE Family Controller”  IS the ethernet connection

You can ignore the WAN Miniport (PPPOE)”, , that is only used when making a direct Internet connection from the pc I.e NOT via a router. 

[#9]

@MisterW Thanks. That makes sense now why the WAN Miniport was asking for authentication. No worries about it not appearing in Device Manager then.

[#10]

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@Colpeper1944 wrote:

Fair comment on the PC (which recently turned 12)

Just a random thought, but something I would try if this was my problem.

Given that the PC is 12 years old, and the network port stopped connecting for no apparent reason,  I'm wondering whether the motherboard CMOS battery (typically a replaceable CR2032 coin cell)  could be at the end of life  and 'might' have started to corrupt the 'non-volatile' BIOS memory settings - which will include how the hardware ports (such as the network interface) interacts with the operating system.

My thought is that if the BIOS has 'lost' the relevant ethernet hardware setting,  that Windows might be booting and recognising that the "Realtek PCIe GBE" ethernet hardware exists within it's IO address space,  but Windows ability to interact with it via the BIOS 'could' have become disabled ?

In the first instance, can you reboot the PC and get into the BIOS menus and check whether the network interface settings look reasonable, and that the network interface is at least "Enabled" ?

If it was me I would photograph (or otherwise record) all of the BIOS menus and settings, power off the PC and remove the mains cable, press and hold the power button for ten seconds to discharge any residual voltage in the power supply, change the motherboard CMOS battery for a new one, do a full BIOS reset (either using motherboard jumper pins, or select "Reset" or "Optimised defaults" option from within the BIOS menus), then reboot into the BIOS and again go through all the BIOS settings and either set them to their original setting or something appropriate.

[#11]

I have just reloaded my guest Win 7 on my vbox system, an ipconfig reveals, with no cable connected.

This what you should see with a network cable connected and the wifi adapter paired to a wireless network

HTH.

[#12]

@Anonymous Thanks for that idea, which certainly sounds plausible. Must admit that I have never even opened the base unit, so some spring cleaning will probably be needed in there too :).

Nevertheless, from your description, that should even be within my competency, and I already have a supply of that battery type.

Will have a go later today or tomorrow.

[#13]

@Anonymous In BIOS Integrated Peripherals:
Onboard LAN Controller was Enabled
Onboard LAN Option ROM was Disabled.
I changed latter to Enabled, but it seems to have made no difference.

Could try the battery replacement later (probably worth doing anyway, as I have loads of those batteries sitting doing nothing).

One thing I was considering, though, is the following. Any thoughts?

https://www.amazon.co.uk/Cable-Matters-Ethernet-Adapter-Supporting/dp/B00ET4KHJ2/