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

It seems that I can't open all Microsoft pages (microsoft.com, support.microsoft.com etc) but pinging Microsoft's IP works (65.55.21.250).

even opening Microsoft pages with the IP's works http://65.55.21.250/en/us/default.aspx

The hosts file is clean, no signs of bad entries.

any help?

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marked as duplicate by KronoS, studiohack, Ivo Flipse Jan 25 '11 at 1:34

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

    
Change your DNS server, flush your DNS caches, get rid of malware. –  Daniel Beck Jan 24 '11 at 9:13
    
Maybe u are using opendns.com or some other dns. –  Kangarooo Jan 25 '11 at 1:21

2 Answers 2

It sounds like one of the following:

  1. Your DNS cache is corrupt
  2. Your DNS provider is not working properly
  3. You have malware

So:

  1. Go to a command prompt and do ipconfig /flushdns.
  2. Try using Google DNS at 8.8.8.8 and 8.8.4.4 -- I can access Microsoft sites with this DNS provider.
  3. Do a scan of your system. My preferred anti-malware scanners are Malwarebytes and SuperAntiSpyware, and my preferred free anti-virus is Avira AntiVir or MSE (or if you're willing to pay, NOD32, or you could just boot into a live environment and use their online scanner). However, scanning for viruses in an infected system is flawed at a fundamental level, because it relies on the operating system to not lie to the anti-virus. It is usually better to boot into an environment that you know to be clean (I have one made for this purpose myself -- I have had good experiences with BartPE), and scan from there.
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hmm, n.1 & 2 didn't work...it seems i can't reach the links for the antimalware you sent me...that's definitely a malware... i'll update the question as soon as i've got some results from the anti malware/virus ! –  user64474 Jan 24 '11 at 9:39
    
no luck using Malwarebytes' Anti-Malware, it found some malware but the problem is always there....is there something else i can do ? –  user64474 Feb 1 '11 at 9:59

The other possible reason is that you have a proxy set somewhere upstream that's filtering out the DNS resolution. My company provides that sort of "service", blocking various named servers (as an example, anything that dyndns.org serves out), but not the IP addresses that those hosts eventually point to. For example, I can get to my home machine if I know what my router's IP address is (external IP address - aka the one that my ISP gives me), but I can't get to it through my dyndns.org domain name.

However, that will depend on whether you've actually got that kind of service between your machine and the wild internet.

edits:

It is feasible that since security related sites provide "untested" software (by a giant multinational corporate site), that they may blanket block all of .microsoft.com to prevent it's users from downloading said "untested" patches. Yes, this happens. Particularly by overzealous Security Departments whose primary purpose to the company appears to be to shout "NO" while banging fists on a desk. Similar story for anti-malware sites. While it is almost always misguided, the situations eventually (but can take literally years) work themselves out. I have personally seen this sort of scenario occur in my company - we're a very large company that develops software, among other things.

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That's somewhat unlikely if the only sites he's noticed it happening on are Microsoft and antimalware-related sites... –  Matthieu Cartier Jan 25 '11 at 11:24

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