[Gllug] DNS verification (slightly OT)

[Peter Corlett]

On Fri, Apr 17, 2009 at 03:10:13PM +0100, James Courtier-Dutton wrote:
[...]
> Note TTL of 2 days. You will have to wait 2 days for the new change to be
> flooded.

DNS doesn't quite work like that.

Queries using an empty cache will not see cached records, and will
immediately see updated records. However, some clients don't follow the TTL
and use their own cache timeouts - up to and including "never expire" - and
so you'll find that some take rather longer than two days to notice the
changed records.

In practice, clients usually start going to the right address reasonably
quickly after broken DNS has been fixed, but with a few annoying stragglers
still looking in the wrong place over a week later.

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