failover

I'm testing wackamole for ip failover and running into some problems.  I've
got spread working on both machines just fine.  I want to have two machines,
but one address that they trade back and forth depending on who's up.  I got
the first machine to create the vip and it works dandy.  The second machine
is on a different subnet, but as I said CAN talk spread-to-spread.  I made
the second machine's wacamole.conf identical to the first's, which was a
mistake...it took over the address, but the other box didn't give it
up....or maybe I just didn't let it run long enough?  Anyway, in the readme,
it says "number of virtual ips that wackamole manages can be less than
number of machines that wackamole manages if some machines have config vip
0.0.0.0".  What does that mean?  Does it mean that on the second box, i
don't put the vip as the address I want it to take over?  or if it has
multiple vips and ONE of them is 0.0.0.0 it's like a switch?  What does my
config need to look like to have two machines and one vip?