why do I get "No response from server"

Greg Chavez greg.chavez at gmail.com
Fri Jun 23 13:05:20 UTC 2006

On 22 Jun 2006 20:35:37 +0100, Chris Thompson <cet1 at hermes.cam.ac.uk> wrote:
> I am afraid that both my claims were wrong:
>   that the NS records in the zone were different from the ones
>   at the delegation point (I had picked the wrong set of NS
>   records from the authority section of a reply)
>   that mail1.ccs.bbk.ac.uk was not authoritative for lkl.ac.uk
>   (its not authoritative for bbk.ac.uk which the CNAME points
>   into, but so what)
> That will teach me to post too fast (maybe). Apologies.

Whenever some name servers cache a RR for a zone positively while
others cache negatively, the cause always seems to be a TTL issue or a
lame/dysfunctional delegation.  So, usually follow the same
troubleshooting process as Mr. Thompson, looking for the bad name
server.  In fact, *appears* that the mail.ccs.bbk box is to blame.

But its not to blame. It returns the CNAME for www.ilk.ac.uk.
However, its authority section shows the root servers.  How does that
happen?  Our Infoblox servers will omit the authority section if
configured to return minimal responses, but give out the root servers?
 When I first saw the query response, it looked like an iterative
brush-off.  Is this broken?  Broken but benign?

; <<>> DiG 9.2.4 <<>> www.lkl.ac.uk @mail1.ccs.bbk.ac.uk
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 1848
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 13, ADDITIONAL: 0

;www.lkl.ac.uk.                 IN      A

www.lkl.ac.uk.          10800   IN      CNAME   thor.dcs.bbk.ac.uk.

.                       3600000 IN      NS      J.ROOT-SERVERS.NET.
.                       3600000 IN      NS      K.ROOT-SERVERS.NET.
.                       3600000 IN      NS      L.ROOT-SERVERS.NET.
.                       3600000 IN      NS      M.ROOT-SERVERS.NET.
.                       3600000 IN      NS      A.ROOT-SERVERS.NET.
.                       3600000 IN      NS      B.ROOT-SERVERS.NET.
.                       3600000 IN      NS      C.ROOT-SERVERS.NET.
.                       3600000 IN      NS      D.ROOT-SERVERS.NET.
.                       3600000 IN      NS      E.ROOT-SERVERS.NET.
.                       3600000 IN      NS      F.ROOT-SERVERS.NET.
.                       3600000 IN      NS      G.ROOT-SERVERS.NET.
.                       3600000 IN      NS      H.ROOT-SERVERS.NET.
.                       3600000 IN      NS      I.ROOT-SERVERS.NET.

;; Query time: 137 msec
;; WHEN: Fri Jun 23 08:41:53 2006
;; MSG SIZE  rcvd: 269

--Greg Chavez

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