After fresh Armbian isntallation is board sometimes disconnecting form Ethernet. And only complete restart helped without access to console. I applied following to try to avoid id:

• Use passive heat-sink (~60°C) with some fan (~30°C)
• Use proper power supply 5V/2A
• Reinstall network-mamnager

   sudo apt-get purge network-manager
   sudo apt-get update
   sudo apt-get upgrade
   sudo apt-get install network-manager