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Date: Mon, 17 Dec 2001 09:49:19 +1000 (EST)
From: Colin Campbell <sgcccdc@citec.qld.gov.au>
To: Jeff Lasman <jblists@nobaloney.net>
Cc: <freebsd-isp@FreeBSD.ORG>
Subject: Re: Using DNAT and DNS round-robin
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Hi,

On Sun, 16 Dec 2001, Jeff Lasman wrote:

> Derrick John Klise wrote:
>
> > IIRC, something like:
> >
> >   monkey.example.net    IN A   192.168.0.1
> >                         IN A   192.168.0.2
> >                         IN A   192.168.0.3
>
> Thanks.  Finally found it on page 259 of DNS and Bind.
>
> > > Is there a way to handle high-availability strictly in DNS?
> >
> > Possibly; I'm unaware of one if there is, though.
> >
> > If you're not too worried about the TTL problem, you could set up a monitoring
> > program to remove an entry from the rotation if it's corresponding address
> > becomes unavailable, then add it when it comes back up.
>
> That's exactly what we're planning on.  Along with very low TTL.  Won't
> help with AOL, Earthlink, etc., though <frown>.

There used to be (still is? - cou;dn't find it) a paper on the ISC web
site (www.isc.org) exlpaining why using DNS for HA was pointless. If
memory serves, the main reasons were

- most browsers cache DNS lookups and so a system that goes down will
  simply appear as unreachable to the browser.

- most browsers ignore TTLs.

Colin


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