Bill Hance on 9 Feb 2009 14:32:50 -0800

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Re: [PLUG] reducing DNS expiry value

minimum TTL is set to 3D for all my domains.
I'll bump it down to 1H at least 3 days before the address change.

> On Mon, Feb 9, 2009 at 5:19 PM, Bill Hance <> wrote:
>>  I am going to be changing the IP address of a web and email server.  I
>> also serve the DNS for the domain.  Is it the BIND "expiry" value that I
>> want to reduce to something like one hour in advance of the change?
>> There are configurable values for refresh, retry, expiry, and minimum
>> TTL.
>>  I set the expiry value from 4W to 1D for all my domains a few weeks
>> ago,
>> and want to make sure I'm on the right track.  If I understand the
>> process correctly, a couple of days prior to the change, I could change
>> the expiry value to 1H.
> The expiry value in the SOA record governs how long secondary DNS
> servers will continue to keep zone data is the primary server becomes
> unreachable.  Recommended value is 4W.  In the example you give above,
> setting the expiry to 1H would mean that if your primary DNS server
> were to say, go offline due to a natural disaster, after 1H the
> secondary DNS server would purge its own records of that domain,
> essentially leaving your domain unresolvable.  That is very bad.
> I think you mean the TTL values, which are usually stored with each
> individual record. (though there may be a default TTL set for the
> domain)  Setting them to 1H (or less) is generally a good idea when
> switching IP addresses.
> -- Doug
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