Sites I'm unable to reach include:
What does unable to reach mean? You get an error? it times out? what exactly happens?
When did this problem start? Were you ever able to load any of those sites?
Sourceforge is probably the simplest of the sites you listed, so lets use that for testing..
from a cmd window run nslookup sourceforge.net You should get something like
Name: Sourceforge.net
Address: 216.34.181.60
if that works, you probably don't have a DNS issue.
Next, try sending a basic request to the site by connecting to port 80 and sending GET /
justin@media:~$ telnet Sourceforge.net 80
Trying 216.34.181.60...
Connected to Sourceforge.net.
Escape character is '^]'.
GET /
HTTP/1.0 302 Found
Location: http://sourceforge.net/
Server: BigIP
Connection: close
Content-Length: 0
Connection closed by foreign host.
This is a good test because it ensures that you can connect to the web server, and the response is small so it will not trigger an issue with large packet sizes.
next, try sending a valid request for the home page by connecting to port 80 and sending
GET / HTTP/1.0
Host: sourceforge.net
followed by enter twice.
At this point one of 3 things will happen:
- You'll get nothing back. This usually points to an MTU problem, but MTU issues are pretty rare these days, and you wouldn't be able to load much of anything if this was your problem. Do you even have a PPPoE based connection? Those are generally the only types of connection that have a strange MTU these days.
- You'll get a few packets back and then it stops mid-html stream. This usually points to a problem with ECN or tcp window scaling.
- You get the whole page back ending with
</body> </html>
If this happens then you don't really have a problem, at least not with sourceforge.net
You didn't say which operating system you were using, other than that it is probably windows since you have IE... If it is Vista or 7 tcp window scaling might be your problem.
They key point is to first figure out what the problem might be, then make changes, not the other way around.
It might be worthwhile to run the Netalyzer: http://netalyzr.icsi.berkeley.edu/index.html
It runs a lot of basic connectivity tests including dns and http.
Ok, so you can't even connect to port 80, this is very interesting. If the dns lookup worked, and got the right IP, but you are unable to connect to port 80, that rules out all of MTU,ECN,tcp window scaling. just to confirm this, can you repeat that test with some more sites, both working and non-working.. telnet google.com 80, telnet superuser.com 80. etc.
I forget if windows prints the 'Trying 216.34.181.60' line? if it doesn't, it might be a good idea to run the nslookup first, then telnet directly to the IP to make sure you are connecting to the right host.
Do all of your machines run windows 7? Are they all running the same software, like maybe an AV program that includes a firewall? It might be a good idea to try a live linux cd/usb image.. even one of the tiny ones like damn small linux would suffice. If you have the same problem running off a clean linux system connected directly to the modem, there isn't much you can do and I would call your ISP.
Also, if you could answer the
'When did this problem start? Were you ever able to load any of those sites?'
questions, they would help narrow down what the root cause of this could be.
And run the netalyzer thing, it might shed some light on the problem.
A downvote - really? – IniTech – 2010-03-06T18:53:58.173