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Posted by Stuart Miller on July 29, 2007, 11:53 pm
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>> If the machine is sitting behind a NAT router is the ping test valid?
>>
>> I thought that the router under normal circumstances is the device that
>> will react to the ICMP traffic, and no machine behind the router will
>> react to the ICMP traffic.
>>
>> When a router or FW appliance has the ability to set rules to stop ICMP
>> traffic, just what is happening? Is the device just not responding or
>> what? What is the device doing?
>>
>> The reason I am asking is I got someone that's asking does he have to set
>> the personal FW to block ICMP traffic behind the NAT router, because of
>> this Gibson's ping test.
>>
>
> Most router's have an option to block WAN requests(ICMP). Depends on what
> is selected. Further more when you request a test from sites like GRC it
> typically pings/tests the WAN IP not the LAN IP of the computer your are
> logged in from. If it's only pinging the WAN IP that means its attempting
> access to the router and has nothing to do with any firewall you might be
> running on your computer.
Agreed
Any outside site, GRC or a hacker's, has no idea of the internal
(192.168.0.xxx) address of the actual computer, and therefore cannot
possibly ping it. The exception is if the filewall specifically allows 'pass
through' traffic such as DMZ, but in this case, the WAN ping is 'translated'
to a LAN ping, and back when responded to.
Ping tests are valid (and often useful) inside your LAN, so I always allow
the computers here to respond to them.
> Now if you are not behind a router and directly connected to modem then a
> test would attempt connection to your computer's IP and the OS or any
> personal firewall would affect results.
Thi is one (of many) valid reasons to have a router/firewall device when you
have only one compter using the internet.
Stuart
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