[olug] DNS Cut Over -- TTL vs. Expires

[Rob Townley]

DynDns.org uses TTL of seconds

On 2/14/07, Sean Kelly <smkelly at zombie.org> wrote:
>
> On Wed, Feb 14, 2007 at 11:21:05AM -0600, Jeff Hinrichs wrote:
> > I am confused between Time To Live (TTL) and Expires. (that is what
> > happens when you only occasionally have to monkey with your DNS servers
> > ;[) Do I need to decrease both of them or just one or the other?
> > Currently:
> >
> > TTL = 38400 seconds
> > Expiry = 604800 seconds
>
> The expiry number tells other secondary/slave nameservers how long they
> should service requests for your zone when they've not been able to
> contact
> the primary and get updates within the refresh/retry periods. This only
> applies to secondary/slave nameservers.
>
> The TTL is the time-to-live for each RR by nameservers across the Internet
> as they resolve and cache records for your zone. This is the one that has
> a
> greater impact on your zone, assuming your primary nameserver doesn't
> vanish a lot. Is is this value that really controls how long it takes for
> the Internets to notice a change to a RR.
>
> I've had TTLs dropped to as low as 5 minutes during periods when we know
> we're about to transition some critical service. Our standard TTL is 86400
> (1 day), so we'll drop the TTL to 300 a day or two ahead of our change and
> then push it back up after the change.
>
> --
> Sean Kelly          | PGP KeyID: D2E5E296
> smkelly at smkelly.org | http://www.smkelly.org
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