Just for grins... can you try disconnecting the ethernet cable and connect over wifi to see if the issue persists. That would point to the switch and cables as issues perhaps.
Another idea... in the Network pane try removing the ethernet entry altogether then add it back and set it up again.
OK - disconnecting, then reconnecting the ethernet cable WORKS!
I'm not sure whether or not that points to a cabling or switch issue, since the same cabling and switch worked fine before installing OSX Mavericks. Regardless, I'll try bypassing the gigabit switch and plug in a direct cable to the router, just to see if that works.
It seems to me that something changed with OSX Mavericks. There is a new "issue" with "waking up" from the sleep mode.
I'll try removing/re-installing the ethernet entry also. Since I have a have a work-around now (although clumsy), I don't want to mess things up more than they are.
"The enemy of
good enough is
better ... "
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Look at the IP listed when this happens. It sounds like possibly the system is not connecting to the network DHCP server and self assigning an IP address, so it is not "truly" connected to the network, but in reality creating its own local network.
I looked at the IP address before the computer goes into sleep mode, then after waking up, then after disconnecting and re-connecting the ethernet cable. Result: the computer has the same IP address (in the local network). If I understand this correctly, the same local IP address is re-assigned even after re-connecting via ethernet. This must be the next free address in the available list of local IP addresses that the router's DHCP feature uses.