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I'm wondering if anyone has ideas on this one, since it's a first for me. I can access the internet just fine with a browser, but using PING or TRACERT from a command prompt just shows requests timing out once they leave my network.

To take some variables out of the equation, I tried reducing my network infrastructure down to just the Comcast cable line coming out of the wall connected to a Linksys BEFCMU10 v4 cable modem which went directly to my Windows 7 laptop with no software firewall, and the issue was still present.

Again, I'm browsing the internet (like posting this question) just fine, but can't ping anything (including this site right now) without all the packets getting lost.

I'm not blocking ICMP on my side, and I don't suspect Comcast is systematically blocking it all the sudden. What am I overlooking?

sXe
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4 Answers4

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A lot of sites may choose to turn off ping response for security reasons, but are still accessible through the limited number of ports that are opened (like 80 for http and 443 for https). Here's some documentation for Linux: http://www.linuxhowtos.org/Security/disable_ping.htm

So in summary, being unable to ping something doesn't mean that you have network issues.

Hope this helps!

JW8
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It turned out to be the cable modem at fault, and a hard reset of that component seems to have straightened it out. In retrospect, since I removed every component of my network except the cable modem and a single laptop to simplify the test, it probably should have been more obvious at the time that it was the culprit.

sXe
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Your router can filter ICMP-packets from external world. If you can login to router and try to ping from it's shell it can give you some hints

Lazy Badger
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It could be caused by the weirldness of windows 8.1. I try to block or allow windows process to test which is needed for internet to run. I endup unable to determine which process is correct one. Sometimes after I blocked some process, the web browser and ping works fine until PC restarted. Sometimes, no change to the process, but After I restarted pc, web and ping not weoking. sometimes, no change to the process, but After I restarted pc, ping not works, but web works. sometimes, no internet works until I disabled my firewall and restart it, then I have to restart firewall everytime I restart PC for internet.

There is a possible explaination that Microsoft is remote controlling your internet accesss through certain process in your PC, if you interfered with those process, you can not access internet until you'd been granted again!

yyy
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