**** IMPORTANT ****

Before you update firmware to Version 1.38 or later
Please do following procedures once to make sure the ethernet will works after firmware updated.

1. open browser-based console.
2. enter the System Controls > EtherNet Config from the menu list on left side. 
3. check the "Confirm The Operation" box at the end, then click the 'Submit' icon to save settings.
 
The V1.38 firmware supports enable/disable ethernet function. 
when you set the port number to 0, firmware will automatically disable it.
 
and because this is a new function, the default port setting value stored in NVRAM is 0. 
so you must save the correct port number once to make sure ethernet will not be disabled after you update the firmware to Version 1.38.