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I am pinging myself and I get replies as normal.

But when I ask my friend from another house to ping my IP, he doesn't get replies.

How is this possible? The modem is on and the IP has not changed. I reset the modem back to its factory settings and still nothing. This started happening three days ago when I had a major power supply failure.

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Have you called your provider? – N4TKD Sep 16 '11 at 20:14
no... i think its modems fault – gorksybinary Sep 16 '11 at 20:35

Simple, your firewall or router is blocking pings. The windows XP firewall, for example, has an option to allow ICMP REQUESTs or RESPONSEs, and no doubt Vista or 7 have same/similar option. Almost certainly your windows firewall is blocking it by default. It's perhaps unlikely that your router is blocking it but I suppose that's possible too. Try pinging yourself from another computer to test if it's your windows firewall. That'll help diagnose what is stopping it.

If you can ping yourself from another computer in your house, then.. What's your model of router? It's worth looking up see if you find anything about it it may be that is blocking it. possibly.

Also obviously make sure you're using your private ip when you try to ping, and your friend is using your public ip when they try. (Though if your router supports NAT reflection then apparently that means you can use your public one.)

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Most routers also come with ICMP blocking by default as a safety feature. You can go into the browser webpage for the router and find the option to turn it off. To get to the browser webpage, just type your router's IP into the address bar in any web browser. Make sure to enable it again when you're done! It's a very important safety feature to prevent bored hackers. – Duall Sep 16 '11 at 20:34
@Duall well i'm sure a lot of security people aren't bothered if somebody can ping their machine.. it'd still come up with a different scan. but could help hide away I suppose. – barlop Sep 16 '11 at 20:40
It's more for the average home user. Takes them off the radar for things like Grimm's Ping. Even businessess generally don't want to be on the radar for that. Just because something is secure doesn't mean you want to advertise it as a challenge. =) – Duall Sep 16 '11 at 20:46

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