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I've been struggling with these problem for months. It happens randomly and it happens on Ubuntu only (12.04). It's about my hosted company website.

Some facts:

  1. I can ping it
  2. I can traceroute it
  3. I can dig it
  4. I can make a nslookup

But whenever I try to open it in Chrome it won't open. I also tried using polipo but got same connection time out issue.

I'm connected through a LAN network and I'm experiencing no problem with any other website.

Is there a more accurate debugging technique I'm missing other than pinging/tracerouting, etc.?

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  • Temporarily solved it by using polipo + tor
    – S.C.
    Jun 27 '13 at 9:13
  • can you put the steps as an answer so future visitors know how to solve it?
    – Alvar
    Jun 27 '13 at 10:44
  • Here are several answers on Ask Ubuntu explaining it: askubuntu.com/questions/201185/…
    – S.C.
    Jul 1 '13 at 12:27
  • Are you using a proxy?
    – Braiam
    Dec 12 '13 at 21:22
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  1. Run tcpdump using something like this:

    tcpdump -nieth0 -s0 -w/tmp/dump.pcap port 80 or icmp
    

or if you are not logged in as root

    sudo tcpdump -nieth0 -s0 -w/tmp/dump.pcap port 80 or icmp
  1. Attempt to access the website.

  2. Press Ctrl+C on tcpdump and then use the wireshark program to examine the capture file (/tmp/dump.pcap). You can find Wireshark in the software centre.

  3. Do the same for a website that does work, and look for relevant differences.

  4. Do the same but at the hosting end.

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Eliminate an MTU problem by pinging with increasingly large packets using ping's -s option, all the way up to 1492. If it turns out that large pings don't work, then something along your path cannot handle 1500-byte packets but is blocking the fragmentation needed packets from coming back.

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    Alternatively the tracepath command might help automating this process.
    – lgarzo
    Jun 27 '13 at 9:11

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