check Availability before sending response

[Ken DBA]

Hello,

Is there any way to make Bind check the server's availability before send back responses to clients?

ie, given the domain name www.site.com was pointed to 1.1.1.1 and 2.2.2.2 in Bind.
When a client query for www.site.com, Bind will check the health status for these two servers. If one is unavailable,Bind shouldn't direct client's requests to it.

I know F5's 3DNS can do it well.But rather than 3DNS, is there any free way for this purpose? Thanks.


Ken.