Thanks for the responses, guys!
16again, I didn't realize until your comment that what I drew looks exactly like an IC interconnect, lol. I thought I was just drawing a block diagram...
I am not familiar with VRF, I will have to look into this further.
Aaaargh, yes that is likely what we may have to do then.
To make it even more complicated, the UUTs need to be switched through several completely different modes, where they will have completely different IP addresses (in each mode). The case I have described above is the only one that wasn't working with a "normal" (non-NAT) switch set up.
Configuring the NAT as described above, (with 8 ERXs) should still allow everything to communiciate "normally" if they had 192.168.x.x addresses on the same subnet in other modes, correct?