Ubuntu (dual boot Windows) Ethernet Not Connecting/Detecting

The bible of network connection problems

The best place to start is with your favorite bible of network connections like this (wiki.archlinux.org - Enable WOL in Windows driver) from ArchLinux.

Although there are dozens of things you can try:

1 Check the connection 2 Set the hostname
2.1 Local network hostname resolution 3 Device driver
3.1 Check the status
3.2 Load the module 4 Network interfaces
4.1 Device names
4.1.1 Get current device names
4.1.2 Change device name
4.1.3 Reverting to traditional device names
4.2 Set device MTU and queue length
4.3 Enabling and disabling network interfaces 5 Configure the IP address
5.1 Dynamic IP address
5.1.1 systemd-networkd
5.1.2 dhcpcd
5.1.3 dhclient
5.1.4 netctl
5.2 Static IP address
5.2.1 netctl
5.2.2 systemd-networkd
5.2.3 dhcpcd
5.2.4 Manual assignment
5.2.5 Calculating addresses 6 Tips and tricks
6.1 ifplugd for laptops
6.2 Bonding or LAG
6.3 IP address aliasing
6.3.1 Example
6.4 Change MAC/hardware address
6.5 Internet sharing
6.6 Router configuration
6.7 Promiscuous mode 7 Troubleshooting
7.1 Swapping computers on the cable modem
7.2 The TCP window scaling problem
7.2.1 How to diagnose the problem
7.2.2 Ways of fixing it
7.2.2.1 Bad
7.2.2.2 Good
7.2.2.3 Best
7.2.3 More about it
7.3 Realtek no link / WOL problem
7.3.1 Enable the NIC directly in Linux
7.3.2 Rollback/change Windows driver
7.3.3 Enable WOL in Windows driver
7.3.4 Newer Realtek Linux driver
7.3.5 Enable LAN Boot ROM in BIOS/CMOS
7.4 No interface with Atheros chipsets
7.5 Broadcom BCM57780
7.6 Realtek RTL8111/8168B
7.7 Gigabyte Motherboard with Realtek 8111/8168/8411 8 See also

We'll start with the most likely based on limited information given that the network card works in Windows but not Ubuntu. This is outlined in the next section.

Windows disables NIC (Network Interface Card) on shutdown

When a BIOS feature known as Wake on LAN (WOL) is disabled your NIC will have no blinking LED's indicating connection and no connection to your router. Windows can disable your NIC on shutdown. To prevent this from happening on Realtek cards under Windows XP (example) use:

Right click my computer and choose "Properties"
--> "Hardware" tab   --> Device Manager
 --> Network Adapters
  --> "double click" Realtek ...
   --> Advanced tab
    --> Wake-On-Lan After Shutdown
     --> Enable

This may not solve the OP problem because exact details are not given. However there is a high degree of confidence that one of the other solutions on this web page will solve the problem.

I found this website helpful running Ubuntu 18.04 on Alienware M15 with the Killer Wireless AX1650, it's a guide for installing the driver. Note that secure boot must be disabled. The guide applies for Ubuntu 16.04 / 18.04 / 19.04. https://support.killernetworking.com/knowledge-base/killer-ax1650-in-debian-ubuntu-16-04/

As of 10/24/19, the website's instructions read:

Enter the following commands into a Terminal one line at a time.

Step 1 – Download the Latest Git and Build-Essential packages

sudo apt update
sudo apt-get install -y git
sudo apt-get install -y build-essential

Step 2 – Download the Iwlwifi-Firmware.git repository

git clone git://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git
cd linux-firmware
sudo cp iwlwifi-* /lib/firmware/
cd ..

Step 3 – Download the Backport-Iwlwifi.git repository Because ‘Make will be producing an Unsigned Driver, you will probably see SSL errors / warnings. This is fine, but this is the reason Secure Boot must be Disabled. If Secure Boot is Enabled your Computer will not use an Unsigned Driver!

git clone https://git.kernel.org/pub/scm/linux/kernel/git/iwlwifi/backport-iwlwifi.git
cd backport-iwlwifi
sudo make defconfig-iwlwifi-public
sudo make -j4
sudo make install

The following command might be necessary to force your machine to use the Driver from boot:

update-initramfs -u

Reboot your machine!

I have had this same problem the last few weeks (Dec. 2020). I dual boot Linux Mint 20 and Windows 10 (this one only for gaming). After a certain Windows update, at every reboot from Windows to Linux the NIC wouldn't work at all. Disconnecting the power cord for a while was a workaround. The UEFI is configured with Wake-on-LAN disabled. The solution came from configuring the NIC in Windows this way:

• Disable Wake-on-LAN
• Disable PME

After changing this settings, the problem was gone: rebooting from Windows to (or powering-off and restarting in) Linux works normally, as it should.