Your best bet may have a Dual IP Congifuation. This involves the machine and DFE being plugged into a switch and looking at your network they would be separate devices instead of having the DFE crossing over to the Xerox machine. The XDA should then see the C60/70 as it's a standalone device on your network.
I found a link with a supporting document that gives you a little more direction: EFI Dual IP.
I found this article for the C60 on XDA and it talks about the fiery. If you are still having issues or this isn't what you need, I suggest that you call into our support department for assistance @ 1-800-821-2797.