Software DNS hghi availability and load balancer solution

[Sergey Voropaev <serge.devorop () gmail com>]

Does any one know software sollutions (free is preferable) like as cisco GSS
and F5 BIG-IP? The main point is that DNS-server (or dns server plugin) must
be able to monitor server availability (for example by TCP connect) and from
DNS-reply depends on it.

I know that it is possible by BIND with set of script. But we are trying to
find more usable solution with frendly interface.

Thanks a lot.