WideIP balancing

Hello.

Basic question for you: I have a new WideIP with two virtual server monitored. I'd like to set up the balancing method so that

1) the DNS reply always with the same IP, until it's available 2) when the first virtual server becomes unavailable, DNS should reply with the second one 3) if none is available, request should be dropped

I'm not sure how to implement this. There is a specific balancing method I can use? I tried the "Ratio" setting the first one to 1 and the second to 0, but it does not look to be the correct way.

Thanks for your help