Hey,

did you consider using BGP [1]? Reading your requirements seems like you're
not doing this for home, that said, two business uplinks supporting BGP
should be payable for a company (not THAT expensive, I went into this once,
too).

OTOH, if basic A-record switching does the thing for you, I'd recomment
using a very low TTL for your record (can go even down to 1 second as
minimum) and install some uptime script that does exactly the check another
poster already replied :)

So long,
Christian Parpart.

[1] http://en.wikipedia.org/wiki/Border_Gateway_Protocol

On Mon, Nov 21, 2011 at 11:03 AM, Pandu Poluan <pandu@poluan.info> wrote:

> On Mon, Nov 21, 2011 at 16:52, Pandu Poluan <pandu@poluan.info> wrote:
> > Hello all, I'm in need of some suggestions.
> >
> > You see, I have 2 Internet connections with public IP addresses, let's
> > say ISP A 11.22.33.44 and ISP B 22.33.44.66
> >
> > Now, I want outside parties trying to connect to "target.example.com"
> > by default resolves to 11.22.33.44, but if ISP A's connection goes
> > down for any reason, the DNS server will instead return "22.33.44.66".
> >
> > The nameserver itself will be located in the company, accessible from
> > the world via "ns1.example.com" = 11.22.33.44:53 or "ns2.example.com"
> > = 22.33.44.66:53. This allows the nameserver to monitor the state of
> > the connections to ISP A and ISP B.
> >
> > I've been perusing pages discussing BIND, and came to the conclusion
> > that BIND is incapable of doing that.
> >
> > Anyone can recommend me a DNS server that has such capability? Or how
> > to implement this ability with maybe Python or (*shivers*) Perl?
> >
>
> To illustrate further, here's the pseudo-language logic that I want to
> implement:
>
> if ( request == target1.example.com )
> {
>  if ( state("ISP A") == "up" )
>  {
>    return "target1.example.com = 11.22.33.44"
>  }
>  else
>  {
>    return "target1.example.com = 22.33.44.66"
>  }
> }
>
> if ( request == target2.example.com )
> {
>  if ( state("ISP B") == "up" )
>  {
>    return "target2.example.com = 22.33.44.66"
>  }
>  else
>  {
>    return "target2.example.com = 11.22.33.44"
>  }
> }
>
> So, as you can see, there are actually two targets, one defaults to
> ISP A (unless ISP A is down, then it 'falls back' to ISP B), and the
> other defaults to ISP B (unless ISP B is down, then it 'falls back' to
> ISP A).
>
> Rgds,
> --
> FdS Pandu E Poluan
> ~ IT Optimizer ~
>
>  • LOPSA Member #15248
>  • Blog : http://pepoluan.tumblr.com
>  • Linked-In : http://id.linkedin.com/in/pepoluan
>
>