HOWTO FIX no link detected Realtek 8168/8169 cards

[noob12]

A number of users have been independently reporting an issue where they see no link detected and/or no link light on their Realtek 8168/8169-based wired ethernet cards when booting Ubuntu on a dual-boot Windows host. The card works in Windows but in Ubuntu it shows no link light and ethtool reports no link detected. (This can also affect you on initial installation of a single-boot system, but after running Windows on the host.)

Several users have now reported that this works for some Realtek 8139 cards as well.

(You can check if you have this type of card by typing the command lspci -nn and looking for your wired ethernet card in the list.)

Here is a fix for the most common causes.

First check that your ethernet cable is connected at boot. There is a known bug in the Ubuntu driver for this card that the cable must be connected to an active link at boot time for the card to work (https://bugs.launchpad.net/ubuntu/+s....20/+bug/86798)

If your ethernet cable is connected at boot time and you are experiencing the no link problem, try this: Shutdown, power down. Unplug your host (this cuts power to the card if wake-on-lan power is maintained). Wait 15 seconds. Plug in. Boot ubuntu.

If that routine works, you are probably affected by the following (excerpt from gentoo wiki http://gentoo-wiki.com/HARDWARE_RTL8168). Note the second and third paragraphs. Then read the Windows-side workaround/solution in the first paragraph.

As of 27 May 2007, in kernel 2.6.21.3, you may experience the issues with the r8169 driver if you dual boot Windows on some systems. Windows by defaults disables the NIC at Windows shutdown time in order to disable Wake-On-Lan, and this NIC will remain disabled until the next time Windows turns it on. The r8169 driver in the kernel does not know how to turn the NIC on from this disabled state; therefore, the device will not respond, even if the driver loads and reports that the device is up. To work around this problem, simply enable the feature "Wake-on-lan after shutdown." You can set this option through Windows' device manager. Edit: Problem with dual-booting with Windows exist also in 2.6.19.5 and 2.6.20.8 kernel, so it is safe to assume that it will concern all 2.6 kernels until the kernel developers update the drivers for RTL8168 to the version that will be able to turn on the NIC from disabled state. (Corey) Second edit: Powering off and unplugging the machine for a few seconds (around 10 usually does it) seems to reset the card, so it will work in Linux again until you boot Windows again.

ADDED NOTE: Please use the poll above only if your situation actually matched the one described here (same symptoms, same hardware and dual boot)