Mini210s can not ping between board

Attachment: ping.jpg (1.93 MB)
I connect Mini210s 2 boards to same switch and setup IP address on both
board (Board A -->, Board B --> I try to ping
board A to B.  It's cannot ping it. So,I connect PC to same switch. I ping
from PC to board A and B. I can ping to A OK. B not OK. I have remove LAN
cable  from B and plug it again. B's OK. but A not OK. What is the problem?
and How to do?  *both board are same image.

> I can ping to A OK. B not OK.

Try pinging from A to the PC and then from B to the PC.

I already known the problem. because,both board same image and same MAC
Address. So,I change one board to another MAC address and reset switch.
Everything It's OK.