DI704 - Can I Use It as A Regular Router?

I want to isolate a section of our network and I have a spare DI704. I
have tried to use it to isolate the subnet, but I can't seem to get it
to connect to the main subnet. I had a crossover cable connecting the
DI704 WAN port to the hub on the main subnet and I could not get it to
connect. I tried fixed IP addresses and DHCP, but no dice. I reset
the DI704, reconfigured every way I could think of. Is there
soemthing special about the WAN port on the DI704? Any and all help
most appreciated.