I have a customer in Michigan who can't access my production SaaS webserver that is hosted on Slicehost. All other companies across the US/Canada/Europe have no problem reaching the site. This problem is occuring intermittantly, and Slicehost customer service says it's a problem with the client's ISP.

I got the IP address of my client, and ping'ing that IP address from my PROD server fails, but ping'ing the IP address from my dev box or our seperate blog server (also hosted on slicehost) works. How do I debug a problem like this? I asked the client to reach out to their local ISP and ask about this problem.

A traceroute shows that the packets are getting stopped on a Comcast Michigan node which is the client's ISP. Is there anything I can do additionally to fix this problem for my client?

  • You could possibly point them at a web-based proxy or one of the many VPN services. Or maybe have them use something like TOR. It isn't ideal, but it may get them working.
    – Zoredache
    Jun 16 '10 at 17:09
  • Can you post the trace-route with the destination IP scrubbed? I ran a trace-route from my Comcast connected computer, and it returns just fine (though it goes from MI->VA->DC->IL->MO to get there).
    – Chris S
    Jun 16 '10 at 17:12
  • Tracing from you to them is not exactly fool proof in determining where the problem exists. The path from you to them and from them to you is not likely to be the same exact path. Have you traced from them to you?
    – joeqwerty
    Jun 17 '10 at 2:35

There is little to nothing you can do. If the ISP has a routing issue on their network that isn't allowing the connection through, then the options are:

  1. Client can complain to the ISP to fix their network.
  2. Client can use a different connection to access the site.
  3. Move the site to another host where the client can access it (not recommended).

Option 1 is usually the best course of action. Unfortunately, the Internet isn't perfect and sometimes there are connection problems. If a traceroute is showing a break within Comcast's network, then Comcast needs to fix it.

  • The resolution came when the client called Comcast and Comcast turned off something called "Smart Packet Detection".
    – MikeN
    Jun 18 '10 at 14:13

Could the isp be intercepting DNS requests ? If so, try using OpenDNS or similar services to see if any change occurs.

  • That would not explain why pinging different IP addresses works for some and fails for others.
    – mfinni
    Jun 16 '10 at 18:04

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