Yesterday I burned a couple of hours playing with the DIR-615 REV A1 that I have had for ages. FreeBSD runs on the Marvell Orion SoC that's inside it now and I thought I'd netboot the box and try to put together an image that can replace my firewall since this little box uses less power and my firewall doesn't need to do *THAT* much.
Unfortunately, it appears as if the network was purposely crippled on this box. Not disabled entirely, but crippled to not work. Sometimes you can get packets out, but generally there's a huge packet loss rate that makes pinging impossible, let alone netbooting.
Talking to other folks that have worked in this area, it appears that this was a deliberate attempt to discourage others from running alternative operating systems on the box.
Since the box will still boot to Linux, there's hope that one can bootstrap the FreeBSD installation from there. When I get some time again, I'll be pursuing that avenue. Maybe I can find the JTAG header for this board and reflash uboot that way, since debugging a new kernel can be difficult to get right in one shot on hardware the kernel has never run on before...
I had planned on publishing instructions for netbooting the thing, but alas, it appears that isn't possible.