After Windows wakes, my GbE network adapter drops to 100Mb

I have an integrated Gigabit Ethernet adapter - a Realtek 8168, I think. Sometime (but not always) when Windows wakens from sleep the adapter runs at 100Mb instead of 1Gb. Disabling and re-enabling the adapter puts it back to 1Gb. A reboot also fixes it (of course).

Is this typical behavior, or do I have something set wrong?

The Windows & Device Manager identifies the device as "Realtek PCIe GBE Family Controller" and says the current driver - version 7.67.1226.2012 - is up to date.

I've have my PC's Ethernet adapter connected to an Ethernet switch for about a year. The switch indicates port speed by different colored LEDs. I don't recall seeing the 100Mb light until a week or 2 ago

Don't know if you'll see it, but in Device Manager right-click on your Realtek network adapter and select Properties.

Then select the Power Management tab, and un-check the "allow the computer to turn off this device to save power", if you have that option.

Now see if you lose your gigabit connection when coming out of sleep.

This is an intermittent problem so it will take a while to see if your suggestion worked. I've made the change and the adapter retained (or re-established) the 1Gb setting after waking, but that is usually the case.

Actually, I'm not sure what should happen when the PC is asleep but the adapter is still powered on. The Ethernet switch shows no connection (no lit LED). That probably means it hasn't seen a packet at a port for some predefined period. That would make sense if the PC was asleep.