odd dns behavior on osx

Tore Anderson tore.anderson at redpill-linpro.com
Fri Jun 18 07:48:18 CEST 2010

Hi Alan,

* Alan Batie

> I've been using www.v6.facebook.com since I found out about it earlier
> this week, and OSX is exhibiting some odd behavior: after a short time
> (the cache timeout period?), gui apps, specifically firefox and safari
> complain "can't find host".  From a terminal window, I can ping6 the
> site, after which firefox and safari can again find it themselves.  Very
> odd...

You're experiencing a known OS X bug.  It will send out the A and AAAA
queries in parallel, and will use the first answer it gets back and
ignore the second one.  You probably get an NXDOMAIN response to your A
request first, and therefore the AAAA response you're actually
interested in gets ignored.

Using ping6 will force an AAAA-only query to be sent, that way you end
up getting the correct response cached in the OS for some time.

See:  http://openradar.appspot.com/7333104

Best regards,
Tore Anderson
Redpill Linpro AS - http://www.redpill-linpro.com/
Tel: +47 21 54 41 27

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