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I'm administering a Fedora 12 box, but am quite new to networking specifics. Recently one of our WordPress apps hosted on our server has stopped being able to perform its auto-update or auto-download of plugins.

Investigating further, I have tried the following:

$ wget wordpress.org
--2010-12-17 11:26:50--  http://wordpress.org/
Resolving wordpress.org... failed: Temporary failure in name resolution.
wget: unable to resolve host address âwordpress.orgâ

Whereas:

$ wget www.google.com
--2010-12-17 11:27:26--  http://www.google.com/
Resolving www.google.com... 74.125.226.82, 74.125.226.84, 74.125.226.80, ...
Connecting to www.google.com|74.125.226.82|:80... connected.
HTTP request sent, awaiting response... 302 Found
Location: http://www.google.ca/ [following]
--2010-12-17 11:27:26--  http://www.google.ca/
Resolving www.google.ca... 173.194.32.104
Connecting to www.google.ca|173.194.32.104|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/html]
Saving to: âindex.html.4â

    [ <=>                                                                                                        ] 9,079       --.-K/s   in 0.02s

2010-12-17 11:27:26 (462 KB/s) - âindex.html.4â

Interestingly:

$ ping wordpress.org
PING wordpress.org (72.233.56.138) 56(84) bytes of data.
64 bytes from wordpress.org (72.233.56.138): icmp_seq=1 ttl=50 time=81.5 ms
64 bytes from wordpress.org (72.233.56.138): icmp_seq=2 ttl=50 time=67.3 ms
^C
--- wordpress.org ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1783ms
rtt min/avg/max/mdev = 67.361/74.448/81.536/7.092 ms

and

$ nslookup wordpress.org
Server:         192.168.2.1
Address:        192.168.2.1#53

Non-authoritative answer:
Name:   wordpress.org
Address: 72.233.56.138
Name:   wordpress.org
Address: 72.233.56.139

nscd has been stopped and flushed. iptables appear to be clean. At this point I have exhausted my limited abilities to diagnose the issue. Can anyone suggest a resolution path?

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What about host wordpress.org –  Mark Wagner Dec 17 '10 at 17:47

2 Answers 2

up vote 0 down vote accepted

Start testing with: wget wordpress.org.

This dot at the end is important If it doesn't fix the problem, do:

  1. cat ${HOME}/.wgetrc
  2. env | grep -i proxy
  3. wget --dns-timeout 1000 wordpress.org
  4. wget --dns-timeout 1000 wordpress.org.
  5. Explain what is the purpose of 192.168.2.1 DNS server?
  6. Show part of named.conf related to caching, forwarding if any.
  7. Do you have there any statement about wordpress.org there? Perform following tests:

dig a wordpress.org. @ns1.mobiusltd.com.

dig a wordpress.org. @192.168.2.1

dig a wordpress.org @192.168.2.1

dig a wordpress.org @192.168.2.1

If this will not give you the answer show /etc/resolv.conf.

Ensure that you have logging section in named.conf and rndc properly set up on the DNS server. Then observe logs, raise trace, dumpdb cache if needed. tcpdump and snoop are your friends. Good luck.

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DNS server is external to my system and I have no control over it. My router (192.168.2.1) is assigned a primary and secondary DNS by my provider, Bell Canada. –  Tom Auger Dec 19 '10 at 7:46
    
have you performed tests 1,2,3,4,and 7 on your workstation? If you don't have control on DNS server all you have to do is try the tests described + tcpdump check. Then look into this, try to understand why the problem appears and let know your provider about the problem. –  plluksie Dec 19 '10 at 13:07

Try wget www.wordpress.org.

If you are curious about what wget is thinking, use wireshark to snoop on its DNS queries.

Looks like a bug in wget.

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