When the printer went to sleep after 5 minutes (default setting) it wouldn't automatically wake up when you sent a print job. The printer appeared offline and you needed to physically press a button on the printer to wake it up. When it was asleep, you couldn't print to it, you couldn't access the web interface, and you couldn't even ping it.
I figured this was crazy that there has to be an easy solution for it. So, I started looking at settings on the printer and nothing seemed to fit. I tinkered with when sleep occurred, but had no success.
I emailed Samsung support and they provided the following link, which described how to disable bidirectional support in the network port. This had no effect.
- Change to a static IP address. I had a DHCP reservation so, this had no effect. However, offline printers can occur when the printer changes IP. So, at least this was relevant.
- Install a new version of the Samsung SyncThru software on my PC. This software wasn't in use.
- Set the sleep timeout to maximum value. This was the final bit where the tech support guy gave up and basically said it would need to print every 60 minutes to avoid needing to wake it up with a button. Not cool.
In the network options there was a setting for Ethernet Power Save that was On. I've turned off this setting and several hours later I'm still able to connect to the web interface and it shows the printer status as in sleep mode.
It makes sense that if this Ethernet Power Save turns off the network connection that you wouldn't be able to wake it up over the network. It's also possible that there is a magic combination of switch and printer that causes the powersave to appear as off to the switch, but some switches may work properly with it. This particular printer is plugged into a small desktop switch in someone's office.