TTL from SOA is smaller than TTL from local DNS!
Edward Lewis
Ed.Lewis at neustar.biz
Thu Apr 12 13:49:44 UTC 2007
At 14:55 +0200 4/12/07, Stephane Bortzmeyer wrote:
>On Thu, Apr 12, 2007 at 08:46:38PM +0800,
> Vishwas <ivishwas at gmail.com> wrote
> a message of 33 lines which said:
>
>> Look at the fourth row, the difference between the TTLs is negative!
>> Under what circumstances the difference between the TTLs should be
>> negative?
>
>For instance, if youtube.com just changed to smaller TTLs.
More likely it is this:
$ dig @e.gtld-servers.net. dns2.sjl.youtube.com. +noall +answer
dns2.sjl.youtube.com. 172800 IN A 208.65.152.137
$ dig @dns2.sjl.youtube.com. dns2.sjl.youtube.com. +noall +answer
dns2.sjl.youtube.com. 3600 IN A 208.65.152.137
The recursive server has only seen the "less trustworthy [RFC 2181]"
address record for this server. Had the latter record been seen, the
TTL would be lower. The 172800 value used throughout the .com zone.
Try this - do a "dig dns2.sjl.youtube.com a" and look at the TTL, you
should see it drop to 3600 and then decrement 1/second. What that
does is "seed" the cache with the authoritative address record.
--
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Edward Lewis +1-571-434-5468
NeuStar
Sarcasm doesn't scale.
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