Which IP addresses should be in the Engines table when running FoE/WAN

Hey guys, I've just finished implementing FoE in our 1xCore & 8 APEs environment and noticed something that seemed odd to me. All servers have 2 NICs, one with dns and all the bells 'n whistles and one with static IP and static route to the other server in the pair but no dns.

I would have thought that the "Engines" table would have the primary IP listed but our table shows the secondary IP. If it wants to use the secondary IP then I'll have to add a bunch of static routes. Which IPs are listed in your Engines table? Which IPs should I have in my table?

Thanks

Mike