Quirky WOL Behavior
 

For a long time I have noticed a quirk with the Wake-On-LAN (WOL) feature.

If the network port is connected to a live switch or router, then the system remembers the WOL option. If the switch or router is unavailable, basically the same as disconnecting the cable, the machine will not thereafter awaken with a WOL magic packet.

The machine always has 5V standby power available and awakens itself when using the real time clock.

The particular machine I tested uses an Asus M3N78-EM motherboard and onboard NIC using the Nvidia GeForce 8300 MCP78S controller. I have Slackware 12.2 installed, using the 2.6.30.10 kernel and the forcedeth driver.

I have tried various scenarios and shutdown settings. I have tried setting WOL (usr/sbin/ethtool -s eth0 wol g) before and after shutting down the network interface. Makes no difference. The behavior is repeatable. The only criterion that matters is whether the NIC is connected to something "live."

Is this behavior caused by the kernel, driver, BIOS, or controller?

Thanks again.

WOL ought to have nothing to do with linux.

WOL should boot system based on bios settings, the problem is that the path to the lan is getting off somehow. Are you scanning the system for the mac before you attempt the wol?

Not sure what you mean by scanning the network. I know the machine's MAC address to which I address the packet. I'm not sending a blanket wol packet.

Something else I just realized. My switch shows the machine's NIC is alive. That is, although the machine won't respond to a wol after being shut down with no router and switch, when I power up the router and switch the switch's LED for that machine's connection indicates enabled.