Look at this :
>ping google.com
Pinging google.com [216.239.39.99] with 32 bytes of data:
Reply from 192.168.10.1: Destination port unreachable.
Reply from 192.168.10.1: Destination port unreachable.
Reply from 192.168.10.1: Destination port unreachable.
Reply from 192.168.10.1: Destination port unreachable.
Ping statistics for 216.239.39.99:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms
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192.168.10.1 is a gateway (router).
Whatever I ping, destination port is unreachable.
I can't connect to IRC, not to P2P networks, can't download with bit torrents. But other's fine.