rcode servfail/adns

Gregory Hicks ghicks at cadence.com
Thu Feb 16 22:39:29 UTC 2006

> Date: Thu, 16 Feb 2006 14:27:26 -0800 (PST)
> From: Gregory Hicks <ghicks>
> Subject: Re: rcode servfail/adns 
> To: Mark_Andrews at isc.org, flatline at greyhat.nl
> Cc: bind-users at isc.org
> > 
> > Are you seriously suggesting to contact RIPE, to 
> > tell them around 4000 of their IPs don't resolve, 
> > just on my host, but they work fine on another? I 
> > think this is not a problem at RIPE, but rather 
> > at my site, which is why I'm requesting help 
> > here. I'm not sure if you fully understand the 
> > problem, but I'm still looking for a solution to my situation. 
> Yes, Mark is quite seriously suggesting this - IF you want the
> ns.ripe.net delegation to get fixed.

The thing you are forgetting here is the way that BIND handles multiple
IP addresses assigned to the same hostname.

Bind uses a "round-robin" like reply structure.  If you have five
addresses, as home.nl does, then the very first time BIND replies, the
reply is in one order.  The next time the response IP addresses are
rotated by one.  The next, by one once again.  After five replies, the
original order and sequence is back.

For instance, name server IP addresses are ns, ns1, ns2, ns3, ...

The first reply to the first query is ns, ns1, ns2, ns3 .  The reply to
the second query is ns1, ns2, ns3, ns .  The reply to the THIRD query
is ns2, ns3, ns, ns1 ... and so on.  This is NOT the first query from
YOU or the SECOND query from YOU.  The queries can arrive from ANYONE
in the WORLD.  You have no idea just which order you are going to get

You may have been the unlucky one that always (mostly always) got "ns"
as the first reply.  This reply just happened to point to ns.ripe.net.
ns.ripe.net FAILED.  (It happens.  Just because they are a registrar
doesn't mean that they don't make mistakes.  Stuff happens.)

Hope this helps.

Gregory hicks


Gregory Hicks                        | Principal Systems Engineer
Cadence Design Systems 
555 River Oaks Pkwy M/S 6B1
San Jose, CA 95134

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