DNS TTLs revisited
Barry Margolin
barmar at alum.mit.edu
Fri Feb 6 00:02:01 UTC 2004
In article <bvuho7$2ath$1 at sf1.isc.org>, Robert Gahl <bgahl at bawcsa.org>
wrote:
> Thus my question: Do earlier versions of BIND lack the ability to recognize
> the specific setting of TTLs on individual hosts?
This is a meaningless question. That's the *only* place that TTLs
exist. If they didn't recognize this, they wouldn't recognize TTLs at
all, since there are no other TTLs to recognize.
The "default TTL" of the zone is not communicated at all in the DNS
protocol, it's only a syntactic convenience used when named parses the
zone file. There's absolutely no way for a client of the server to tell
the difference between explicit per-record TTLs and TTLs inherited from
the default.
Are you sure that your changes have propagated to all your slave
servers? And how long after you changed the TTL on the record did you
do your tests? If it was less than the old TTL, then you're just seeing
records that are still in the caches, because the old TTL allowed them
to stay around for a day.
--
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
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