First when you are having the issue, before rebooting, can you ping google.com? Can you ping the address 184.108.40.206?
220.127.116.11 as well as 18.104.22.168 are two very well known and reliable free publicly available (and pingable) DNS servers owned by Level3 Communications and Google, which also work great as test pings to verify internet connectivity (plus they're easy to remember ;) ).
First even though you've tried mulitple browsers, I'm curious if you can even ping a dns name such as google.com or yahoo.com. If not can you ping one of these public IP's?
* If neither work then possibly something is up with your NIC or the router since a reboot fixes it. Also check option 5 below to verify local routes.
* If you can still ping the public IP's but not the DNS name, then something may be up with the DNS server you're using, in which case, change your NIC to use 22.214.171.124 and 126.96.36.199 as your DNS servers. If this fixed your problem, you may want to check with your ISP about the DNS servers given to you, though feel free to leave these configured if they work; I'm using them right now.
* Now if ping works to both google.com and 188.8.131.52, but you still can not browse the net, then that tells you DNS is working fine and ICMP packets are going, though TCP and/or UDP are are failing which could be caused by a number of things. For starters I'd check the following:
1) At work, do you use a proxy server to connect to the net? If so it may have not cleared out. The proxy settings do not affect ICMP (ping) packets.
In Internet Explorer settings, check the proxy server under the Connections tab and make sure there nothing is checked. Even though you tried three browsers, all of them now use IE's proxy settings so you don't have to change it in each browser and so group policies work throughout.
You may also want to verify the proxy is off directly from registry under:"HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings"
ProxyEnable should be set to 0
2) Check your home router. Verify there are no unwanted access lists or restrictions. You may also want to try rebooting the router and if necessary, resetting it back to factory and re-configuring it. There may be something cached in the router from the previous login that did not clear out for some reason until you rebootied the PC which sent a formal disconnect to the router.
3) As others have noted, because of your comment above about that suspicious "as.addthis" you saw, you may want to run a few more scans such as HijackThis. I'm leaning toward the other causes I mentioned above since you say everything always works good at your work, but you never know. Doesn't hurt to check.
4) Check your local hosts file. Even if google.com or yahoo.com was pingable, if you have a bad local hosts file, you could be seeing an enemy IP. Again, not to likely since you say all is fine at work, but still worth a glance anyway.
The location is: "%SystemRoot%\System32\drivers\etc\"
. The file is named hosts
without any extension and can be opened with notepad.
5) In CMD, type ROUTE PRINT
. This will show the local routes your computer uses to reach outside networks such as the internet. Check if anything looks off here and verify all the routes, especially the default "0.0.0.0" route, are pointing to the correct Gateway and Interface. I doubt anything will be off here if any of the ping tests worked, though still worth a check to verify it's not still showing your work Gateway.
Hope some of this makes some sense and I didnt just ramble on ;) Let me know what you come up with and if you have any other questions or need any more help, I'll be glad to give it a shot.
Edited by Wired68, 05 October 2010 - 09:15 AM.