On Tue, Jan 18, 2011 at 12:42 PM, Sergey Voropaev <serge.devorop@gmail.com> wrote:
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.
Sergey, I have no suggestions that directly answer your question. I'd write a script against bind myself. But if you're trying to fail over a web server, you're walking into a nasty trap. "DNS pinning" obstructs web browsers from finding a server on an alternate IP address regardless of the DNS TTL. The core issue is that allowing a browser running javascript to connect to a server other than the one from which the script came is a gigantic security hole. Someone realized you could do that by changing the IP address the host name pointed to, so now there's a convoluted and not entirely standardized set of rules for when and whether the browser allows it. Net result is that in some cases a user's long-running browser will indefinitely ignore the change you made to the DNS. I've seen such things persist for months. For better or for worse, the way you -reliably- fail over a web server is with routing and middleboxes like a load balancer. Regards, Bill Herrin -- William D. Herrin ................ herrin@dirtside.com bill@herrin.us 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/> Falls Church, VA 22042-3004