f0:fe:6b = Shanghai High-Flying Electronics Technology Co., Ltd
Never heard of them...
So it connects to your wifi, does it get an IP on your network? And then the only thing it sends is that arp? Maybe that is something hard coded in its stuff looking for a firmware update or something or boot options..
While yes 6.0.0.0/8 is a dod address. It is not uncommon for companies to use that space on their own network.. A previous company I worked for (very large msp) used many of the /8 ranges from the dod in their DCs.. Yup some were 6.x.x.x
What you could do - is set up a 6 network and give something that IP, to see what it sends it after its gotten back an answer to its arp. Which may give you some clue..
Other than curiosity to what its actually doing, I would just return it, or have them send a replacement. Did it ever work? Is it old and your just now trying to connect it to the network?