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Super User’s Top Question of the Week [17 Jan-24 Jan]

January 24, 2011 by . 0 comments

Ever seen this?

image

Or how about this?

image

You know that your internet connection isn’t down, because you’ve been able to browse to other sites, but you still cannot access this one site!  What do you do when you think a single site is down?  That’s exactly what Kyle Brandt asked in:

How do I diagnose not being able to reach a specific website as an end user?

If I can generally reach web pages on the Internet but can’t reach a specific one, how do I troubleshoot what the cause is as an end user?

Jeff Atwood gives us the answer.

First, check to see if the site is either down for everyone or just for you by visiting:

http://downforeveryoneorjustme.com

If the site states that it’s down for everyone, the site is down and there’s really nothing more that you can do.  But what if the site is down only for you?  Well it can be several things including a DNS issue and here’s how to check:

  1. Open a command window and ping the site that you are trying to access:image
    This is what it should look like, but if you get an error like this:image
    Then there is a problem.
  2. Run a nslookup against google’s DNS server (8.8.8.8) to see for sure:image
    If you get something like this, then you’ve been able to connect to the server correctly using a different DNS server.If you get this error:
    image
    Then there is an errorYou can also try using GRC’s DNS Benchmark for Windows to test DNS issues as well.
  3. Try running a trace route to the site you are accessing
    image
    This will tell you where exactly the packets are being lost.  You can also use PingPlotter:

PingPlotter (Shareware; Free 30-day evaluation.) which will repeatedly run a traceroute and graph the results, so you can see if you have packet loss or bandwidth problems at any hop on the traceroute.

- Jeff Atwood

Now that’s you’ve done these tests here’s what they mean:

  1. If your ping, nslookup, and tracert are all working but still cannot access the site then there is probably an issue with the browser.  Install and try accessing the site from a new browser to make sure.  (Believe it or not, there are still a few sites out there that solely support IE)
  2. If changing your browser doesn’t solve the issue and a tracert shows an extremely slow spot then there’s probably an issue with your connection.  A contact of your ISP is about all you can do from there.
  3. If your ping doesn’t work but a nslookup does then there’s probably a problem with your DNS server.  If you use the DNS benchmark software, you can select different DNS servers to use instead.  Otherwise you should contact your ISP to resolve the issue.

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