Unless it is the port itself (which is unlikely), the NIC consists of dual-channel chips on the motherboard. The parts are not available in single quantities and working with the surface mount parts requires proper equipment and skill. In short, it's possible but not pratical.
Personally, I think it's time for a new NAS. Even a current ARM machine will be faster than your NVX.
Thank you for your answer. Now the second NIC port is defect also. When I buy a new NAS, will I be able to get access to my data thrue the USB connection?
Without a working network, I have no control of the ReadyNAS nor do I have access to my data. Any suggestions on how to get my data to a new NAS?
Now the second NIC port is defect also. When I buy a new NAS, will I be able to get access to my data thru the USB connection?
The NAS is a USB master; it cannot operate as a USB slave. It is possible to use a console serial port to access the NAS via linux command lines. From there you can manually copy data to attached USB drives. In new x86 NAS this is done with a standard microUSB cable (the connector is hidden under a label on the rear panel).
This is also possible with your NVX, but is more complicated. There is a blog post here that outlines how: https://gist.github.com/davewongillies/6481138 Note this isn't something I've done myself.
Note that if you had configured USB backup jobs that used the backup button on the NAS, it would have been possible to get the data off even without a working network connection.
Any suggestions on how to get my data to a new NAS?
If you purchase a new x86 ReadyNAS (RN300 series or higher), then you can temporarily mount the NVX data volume (read-only) and copy the data off. This can't be done with the arm-based OS-6 NAS (RN100 and RN200 series)
The volume can also be mounted in a standard linux system (often done with the drives connected via USB->SATA adapter(s) ).
