Sometimes users get host unknown
Peter Dambier
peter at peter-dambier.de
Tue Jun 13 12:39:59 UTC 2006
Andrew Watkins wrote:
> Hi,
>
> We have had an ongoing problem that some people (over the world) that
> they can not access our web server, since they do not get an IP address.
>
> I have tested from my home ISP (away from work) and am unable to get the
> same errors. I have tested the DNS from a few web sites www.dnsstuff.com
> , etc and can not pin point any major problem
>
> Our webserver has many addresses
> www.lkl.ac.uk
> www.lonklab.ac.uk
> www.londonknowledge.ac.uk
>
>
> The last report we had from a user was: dig +trace +qr www.lkl.ac.uk
>
> ; <<>> DiG 9.2.1 <<>> +trace +qr www.lkl.ac.uk
> ;; global options: printcmd
> . 47891 IN NS c.root-servers.net.
> . 47891 IN NS b.root-servers.net.
> ;; Received 356 bytes from 165.225.198.2#53(165.225.198.2) in 5 ms
>
> uk. 172800 IN NS NS1.NIC.uk.
> uk. 172800 IN NS NSD.NIC.uk.
> ;; Received 493 bytes from 192.33.4.12#53(c.root-servers.net) in 48 ms
>
> ac.uk. 172800 IN NS ns1.cs.ucl.ac.uk.
> ac.uk. 172800 IN NS ns2.ja.net.
> ac.uk. 172800 IN NS ns3.ja.net.
> ac.uk. 172800 IN NS ns4.ja.net.
> ac.uk. 172800 IN NS sunic.sunet.se.
> ac.uk. 172800 IN NS ws-fra1.win-ip.dfn.de.
> ac.uk. 172800 IN NS ns.uu.net.
> ac.uk. 172800 IN NS ns0.ja.net.
> ;; Received 233 bytes from 195.66.240.130#53(NS1.NIC.uk) in 129 ms
>
> lkl.ac.uk. 86400 IN NS ns1.lonklab.ac.uk.
> lkl.ac.uk. 86400 IN NS mail1.ccs.bbk.ac.uk.
> ;; Received 101 bytes from 128.16.5.32#53(ns1.cs.ucl.ac.uk) in 150 ms
>
> dig: Couldn't find server 'ns1.lonklab.ac.uk': Name or service not known
>
>
> Any pointers?
>
>
> Thanks in advance,
>
> Andrew Watkins
> *****************************************************************************
> Unix Administrator tel: 020-7631 6720
> Computer Science Department fax: 020-7631 6727
> Birkbeck College (University of London)
> Malet Street
> London e-mail: andrew at dcs.bbk.ac.uk
> WC1E 7HX
> http://www.dcs.bbk.ac.uk/~andrew
> *****************************************************************************
>
>
Asking a djbdns resolver I get:
; <<>> DiG 9.1.3 <<>> -t any www.lkl.ac.uk @echnaton
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 21133
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;www.lkl.ac.uk. IN ANY
;; ANSWER SECTION:
www.lkl.ac.uk. 86400 IN CNAME thor.dcs.bbk.ac.uk.
thor.dcs.bbk.ac.uk. 86400 IN A 193.61.29.33
;; Query time: 1663 msec
;; SERVER: 192.168.208.228#53(echnaton)
;; WHEN: Tue Jun 13 14:01:53 2006
;; MSG SIZE rcvd: 74
1 2/3 seconds to answer is not very fast.
Asking a Bind 9.4.0 I get:
; <<>> DiG 9.1.3 <<>> -t any www.lkl.ac.uk @lomi
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 44818
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 1
;; QUESTION SECTION:
;www.lkl.ac.uk. IN ANY
;; ANSWER SECTION:
www.lkl.ac.uk. 85585 IN CNAME thor.dcs.bbk.ac.uk.
;; AUTHORITY SECTION:
lkl.ac.uk. 85585 IN NS ns1.lonklab.ac.uk.
lkl.ac.uk. 85585 IN NS mail1.ccs.bbk.ac.uk.
;; ADDITIONAL SECTION:
ns1.lonklab.ac.uk. 85994 IN A 193.61.29.32
;; Query time: 28 msec
;; SERVER: 192.168.48.227#53(lomi)
;; WHEN: Tue Jun 13 14:07:24 2006
;; MSG SIZE rcvd: 124
but a CNAME is not an ip-address. I have to ask again:
; <<>> DiG 9.1.3 <<>> -t any thor.dcs.bbk.ac.uk @lomi
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 38786
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 3, ADDITIONAL: 4
;; QUESTION SECTION:
;thor.dcs.bbk.ac.uk. IN ANY
;; ANSWER SECTION:
thor.dcs.bbk.ac.uk. 85421 IN A 193.61.29.33
;; AUTHORITY SECTION:
bbk.ac.uk. 359021 IN NS bas-a.bcc.ac.uk.
bbk.ac.uk. 359021 IN NS link-1.ts.bcc.ac.uk.
bbk.ac.uk. 359021 IN NS ns0.ja.net.
;; ADDITIONAL SECTION:
ns0.ja.net. 118707 IN A 193.63.94.20
ns0.ja.net. 118707 IN A 128.86.1.20
ns0.ja.net. 118707 IN AAAA 2001:630:0:9::14
ns0.ja.net. 118707 IN AAAA 2001:630:0:8::14
;; Query time: 48 msec
;; SERVER: 192.168.48.227#53(lomi)
;; WHEN: Tue Jun 13 14:10:09 2006
;; MSG SIZE rcvd: 212
Maybe some resolvers dont follow the CNAME. That may depend on
what information is currently stored in their cache.
Next test
; <<>> DiG 9.1.3 <<>> -t any www.londonknowledge.ac.uk @echnaton
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 43951
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;www.londonknowledge.ac.uk. IN ANY
;; Query time: 137 msec
;; SERVER: 192.168.208.228#53(echnaton)
;; WHEN: Tue Jun 13 14:35:26 2006
;; MSG SIZE rcvd: 43
After only 137 djbdns returns without an ip-address without a nameserver
; <<>> DiG 9.1.3 <<>> -t any www.londonknowledge.ac.uk @lomi
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 17733
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; QUESTION SECTION:
;www.londonknowledge.ac.uk. IN ANY
;; AUTHORITY SECTION:
ac.uk. 600 IN SOA ns0.ja.net. jips-nosc.nosc.ja.net. 2006061260 28800 7200 3600000 14400
;; Query time: 209 msec
;; SERVER: 192.168.48.227#53(lomi)
;; WHEN: Tue Jun 13 14:38:04 2006
;; MSG SIZE rcvd: 104
Bind 9.4.0 has found the authority but not an answer.
--
Peter and Karin Dambier
Cesidian Root - Radice Cesidiana
Graeffstrasse 14
D-64646 Heppenheim
+49(6252)671-788 (Telekom)
+49(179)108-3978 (O2 Genion)
+49(6252)750-308 (VoIP: sipgate.de)
mail: peter at peter-dambier.de
mail: peter at echnaton.serveftp.com
http://iason.site.voila.fr/
https://sourceforge.net/projects/iason/
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