Re: Software DNS hghi availability and load balancer solution

[William Herrin <bill () herrin us>]

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


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William D. Herrin ................ herrin () dirtside com  bill () herrin us
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