No route to host, unless someone is logged in
Probably FileVault2 is enabled on the remote Mac.

After a clean reboot and before entering the FileVault/user password the disk won't be available and subsequently the common network won't be enabled.
After unlocking the disk locally you should be able to discover your Mac and ssh to it.
If the Guest account is enabled in the FileVault mode your Mac might be pinged depending on the network setup (DHCP), but since it is a special 'Safari window only mode' you shouldn't be able to ssh to it.

To reboot a FileVault-enabled Mac remotely enter sudo fdesetup authrestart. This allows you to restart a FileVault-enabled system without requiring an unlock during the next startup. Check this Apple support page for more information.

If FileVault2 isn't enabled i would expect that the sleep and Wake-on-LAN settings aren't properly set.