Configure them exactly identical. Then use Exclusions so that one gives out
the first half of the available addresses and the other gives out the second
half of the available addresses. If you use any Reservations then make sure
they are the same on both server.
If one server goes down you can just delete the Exclusion on the remaining
one and it will keep things going until the first one is fixed. In fact if
half the addresses is enought of keep things going then you won't even have
to delete the Exclusion.