[Solved] WOL (wake-on-lan) no longer works after upgrade to CentOS 7.7

[jimj]

After upgrading from CentOS 7.6 to 7.7 I discovered that I could no longer wake my PC via WOL (wake-on-lan).
I discovered that in CentOS 7.7 my NIC was now defaulting to WOL disabled (in 7.6 it defaulted to "magic packet"). I followed the steps here to enable WOL/magic packet for my NIC with nmcli (nm-connection-editor is the GUI way). At this point I thought my problem was solved but alas, my computer still wouldn't resume from suspend via a WOL magic packet.

In nm-connection-editor I noticed my interface's "Link negotiation" was set to "Ignore". This appeared to be a safe setting, my NIC was correctly negotiating to gig/full. However I decided to see if setting this to auto-negotiate would help, so I ran this command as root (for my "enp3s0" interface):

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nmcli c modify "enp3s0" 802-3-ethernet.auto-negotiate yes

I then rebooted, suspended and tested waking my desktop and it worked! Even better, this has resolved the weird WOL only works after you've resumed from suspend (sleep) once issue I've lived with for years.

One bit of additional info. After following the ArchWiki steps (and rebooting) running ethtool (as root) should show that your NIC is configured for "Wake-on: g" (MagicPacket). For example if your interface name is "enp3s0" your command and output would look like this:

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# ethtool enp3s0 |grep Wake
	Supports Wake-on: pumbg
	Wake-on: g

If "Wake-on" os set to "d" that means it's disabled.

[fpaquet]

Further information can be found in this issue:
https://bugs.centos.org/view.php?id=16486

[jimj]

Further information can be found in this issue:
https://bugs.centos.org/view.php?id=16486

Thanks for sharing. Apparently this WOL issue only affects Realtek NICs like I have (I'm using a Realtek 8111D NIC that's build into my motherboard):

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$ lspci|grep Ethernet
03:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 03)
04:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 03)