check Availability before sending response

[Kevin Darcy]

Ken DBA wrote:
> 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.
>
>   
Roll your own monitoring system and have it modify the DNS RRset via 
Dynamic Update (if you prefer) to reflect which server(s) are up/down at 
any particular time.

That's essentially what all these fancy, expensive GSLB boxes do anyway.

- Kevin