Re: difference between DROPped pings and non existing hosts

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Tobias DiPasquale schrieb:
On 4/26/05, Daniel Lopes <lopsch@xxxxxxxxxx> wrote:

I would like to know how ICMP distinguishes between DROPped pings and
non existing hosts. Both times you don´t get a reply from the
destination host but if it doesn´t reply because it doesn´t exist you
get the correct destination unreachable message if it drops the requests
for example with IPTables you get a timeout. And I haven´t a clue why
this is so.


In the case where you get a destination unreachable message back, its
the router that is responsible for the network on which the machine
you are trying to ping that is responding with that message. When ICMP
is dropped, the packet makes it to the host and thus the router does
not generate a destination unreachable message to send back to you.

Hmm I forgot the hardware address. In the case the router can´t do a address resolution he generates a ICMP error message because he won´t be able to deliver the packet is that right?
Thank´s so far for the reply :).




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