Efficacy of using short timeout values for an A record

[Oliver Garraux]

On Tue, Feb 14, 2012 at 5:59 AM, goran kent <gorankent at gmail.com> wrote:
> Hi,
>
> I need to setup an A record for a machine who's IP might change
> unexpectedly, and I need to ensure PCs out there cache it for as short
> a time as possible:
>
>    host1    300  IN A 10.10.10.10
>
> Does anyone know whether MS windows PCs will in fact honour that 300s,
> then force a re-lookup?  Can I use even shorter values?  eg, 60?
>
> I know this will lead to extra DNS traffic, but this is only for this
> particular case.
>
> Thanks for any comments.
>
> Regards
> gk
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I don't think you'll have a problem with clients not respecting TTL's.
 Some ISP's resolvers might have a minimum TTL, but 300 seconds isn't
all that low.

You might run into issues with some service providers if you're trying
to do something like a 5 second TTL.

Oliver