[FX.php List] [OFF] Question about DNS TTL (time-to-live)

[William Downs]

Broadly speaking, this is correct...

BUT, it really depends on where the other cached records came from - and of course, how long they take can be hours - because a TTL somewhere else may be set much higher...

In other words, other persons around the world may NOT set their TTL to mirror yours :-)


On 11 Oct 2011, at 07:51, Steve Winter wrote:

> Bob
> 
> Also remember that it is now 300 seconds - what was it before…? DNS servers will hold on to their current record (including the TTL) until the previous TTL has expired, so if the DNS had been quite stable and the TTL was up to a couple of days (say) then it'll take that long before the records on any remote servers expire and they come calling again…
> 
> Cheers
> Steve
> 
> 
>> Steady on Bob,
>> 
>> Adjusting your TTL settings did not make you boss of the internet. TTL is simply the equivalent of a "Best Before" date on your milk carton.
>> 
>> What you have done is said to the other servers that come knocking, "Here is the information you need. Take it and don't come back for 5 minutes". Which is as good as saying you will warranty the reliability of your DNS settings for 5 mins, after that you don't guarantee the results. 
>> 
>> I suspect that a good number of other DNS servers haven't ever knocked on your door and those that have done so run on a longer schedule TTL themselves so they may just decide to keep to their own timetable.
>> 
>> Malcolm
>> 
>> 
>> On 10/10/2011, at 9:31 AM, Bob Patin wrote:
>> 
>>> My understanding is that time-to-live in DNS settings determines how long DNS servers will cache a domain name's record before going back to the name servers to check the IP address.
>>> 
>>> I set a DNS TTL to 300 seconds for a domain name, but it didn't update worldwide in 5 minutes. In fact, it's been 6 hours and I'm still waiting.
>>> 
>>> From what I've read, it was my understanding that the TTL setting tells all the upstream DNS servers how long to cache the domain info; am I missing something?
>>> 
>>> Thanks,
>>> 
>>> Bob Patin
>>> Longterm Solutions LLC
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> Steve Winter
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> steve at bluecrocodile.co.nz
> 
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