optional 2nd Ethernet port

Is there a price difference if you get a second Ethernet port?

Yes, the “Standard version†of armStoneA8 offers 1x Ethernet, the “Premium version†offers 2x Ethernet.
Please refer to our product information http://www.fs-net.de/download/…rmStoneA8-A4-Englisch.pdf, see page 2, armStoneA8-512DN2C1G.