Lame delegation to server with cached NS data.

[Kevin Darcy]

Two Dog wrote:

>Hello,
>
>While this is more of a DNS question than a BIND question I do
>appreciate your help with this, as I'm having some trouble
>understanding it.
>
>The domain in question is wecdsb.on.ca when I query it returns an
>answer only occasionally. This domain is not under our control or do I
>have any authority over it.
>
>I did a traversal of the domain at http://www.squish.net/dnscheck and
>saw that one of the name servers for that domain ns4.dm.egate.net is
>"Loop Detected! Probable cause is lame delegation to server with
>cached NS data"
>
>As far as I understand it that means the egate.net name server is
>sending out the request for a question it already has the answer too
>thereby creating a loop.  Would that be correct?  If so what could one
>do to resolve that issue?
>
>I've also tried looking up this domain against other name servers and
>they too occasionally return a timed out result or no host.
>
>How can I educate this customer that the 'problem' in question does
>not exist on our network but his network layout?
>
Calling this a "loop" is I think a little misleading. The wecdsb.on.ca 
domain has been delegated to ns4.dm.egate.net (as well as to 
ns.wecdsb.on.ca), but ns4.dm.egate.net is not authoritative for the 
zone. This is a typical "lame" delegation, then. Most nameservers 
implementations will recognize this lameness and simply ignore what 
ns4.dm.egate.net has to say about the zone. What this boils down to, 
however, is there is exactly *one* working nameserver for the domain 
(ns.wecdsb.on.ca). If that nameserver gets a little busy, or its 
connectivity blinks out temporarily, then the whole domain can become 
unresolvable for anyone who doesn't already have the relevant 
information cached. If the domain owner cares about the availability of 
that zone, they should arrange for at least one other nameserver to be 
authoritative for the zone, and then update the delegation records and 
the NS records in the zone to reflect that redundancy.

- Kevin