DNS records change time

Gregory Hicks ghicks at cadence.com
Mon Feb 6 22:31:30 UTC 2006

> To: comp-protocols-dns-bind at isc.org
> From: "Tester" <CalinGuga at netscape.net>
> Subject: DNS records change time
> Date: Mon, 6 Feb 2006 16:53:49 -0500
> Hi there,
> If I will change some DNS records on my external DNS name server Bind 9, how
> long it will take to propagate around the world, in other words when all
> clients will be able to connect to these hosts whose IPs I changed from
> outside? Thanks a lot, Calin

If this isn't an FAQ, it should be.

The short answer is...  It depends.

It depends on when the last client queried for the old record.  TTL
will keep this answer in the cache for $TTL seconds.

If you have a lo-o-o-o-o-n-n-n-n-g TTL, then it could be awhile until
that client gets the new info.  If you have a short TTL, then ...

As for "... propagating around the world..." this really takes very
little time.  The answer stays on your server until someone queries for
it.  If someone on the other side of the world queries for the info a
microsecond after your zone was updated and reloaded, then propagation
time "around the world" is nil...

DNS is a distributed database with each zone server having the ultimate
answer for that particular zone.  There really is no "updating" to
foreign hosts that takes place.  The only updating is to your
master/slave servers...  All others query for specific records.

Gregory Hicks


Gregory Hicks                        | Principal Systems Engineer
Cadence Design Systems               | Direct:   408.576.3609
555 River Oaks Pkwy M/S 6B1          | Fax:      408.894.3400
San Jose, CA 95134                   | Internet: ghicks at cadence.com

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