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I'm facing a weird problem with some websites. In my network nobody is able to access a particular website, whereas that website is up when I checked it at http://www.isup.me/.

This happens quite frequently in my network. Not only this site, it happens with some other websites as well. But after a day those sites are up again in my network.

What could be the reason behind this? Is there any solution for this issue?

Update: I tried to reach website with IP address by using ping but couldn't successful. I'm using Windows operating system. I tried to access this site on all browsers (chrome, IE, firefox) Our network has a router but we dont have access to it. But I can request my administrator if anything requires to be done.

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Can you reach this website by its IP address? What is the DNS set up for your network or your computer? Have you tried changing it? Which operating system(s) is/are there on your computer(s)? Does your network have a router that you can access? –  slhck Jul 11 '11 at 7:05
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@slhck: I've updated the question, please have a look at it. Can you explain what do you want to know about Dns setup? –  JayaprakashReddy Jul 11 '11 at 7:11
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See what happens with traceroute (tracert in windows), as it should give you some indication of where traffic is stopping at. –  Stephanie Jul 11 '11 at 7:42
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See also - superuser.com/questions/231977/… –  ChrisF Jul 11 '11 at 8:35
    
Unfortunately before I diagnose the problem with all the methods listed in comments and answers, the site came back on my network. But thanks for everyone, I would definitely use all these methods next time when any other site is down only for me. –  JayaprakashReddy Jul 12 '11 at 7:37

3 Answers 3

I think your update that said you could not successfully ping says it all. Occasionally your route (the path along the Internet traffic takes while going through many routers) to a server can be down, anywhere along the way. I have seen this happen many times, even here in the U.S.

A router has gone down, or is temporarily mis-configured, is usually the cause. In most cases, when that happens, it is being closely monitored in a NOC (network operating center). I have been in several big NOC's, and they had everything projecting on a big wall, and when a router goes down, it turns from green to red, and everyone springs into action.

Generally, there is not much you can do personally, other than to wait. If it persists for any length of time, you can try calling your ISP to have them track down the problem, and check with the owner of the faulty router to make sure that they are working on the problem.

Again, if it is persistent (they probably don't want a bunch of calls from home users otherwise), you can use the tracert command in Windows, or traceroute command in Linux to determine exactly where the connection is failing. You could then look up the IP address at http://www.arin.net to possibly get the contact info (it may only give you a top-level owner, not the actual owner is the problem). It may also direct you to another website to get this information for your country.

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If using MS-Windows, running "IPCONFIG /FLUSHDNS" at the DOS prompt can sometimes resolve this problem, but if it doesn't...

The router may need a firmware upgrade (I've seen a few routers over the years that exhibited strange problems like yours that were fixed by a firmware upgrade), or it may need to be replaced if it's failing (it is unlikely that the ISP is causing this problem, although I have encountered a handful of them that did block ICMP traffic which is needed for PING, TRACEROUTE, and similar diagnostic tools) -- you can test this by temporarily using a different router.

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You should check the DNS that you get the same IP address to the webpage as the rest of the world. It's possible your upstream ISP has set up a dummy domain.

Try

  • nslookup www.company.org
  • nslookup www.company.org 8.8.4.4

Also the address should be the same as in your ping output. Ping itself is not very conclusive nowadays as many block it. Try instead

 telnet www.company.org 80 (enter)
 GET / HTTP/1.0 (enter)
 Host: www.company.org (enter)
 (enter)

If your OS doesn't have telnet you can always get putty.

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