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Re: Suggested patch (no ARP ping on localnet with -P0)
From: Andreas Ericsson <ae () op5 se>
Date: Wed, 25 Jan 2006 11:42:02 +0100

Martin Maèok wrote:
On Wed, Jan 25, 2006 at 10:16:00AM +0100, Carl-Johan Bostorp wrote:

I came across a situation where I didn't want nmap to even do ARP ping
on the localnet

Could you clarify the reason?

If Nmap does not send and ARP then the OS will do it instead
automagically ...

On windows, I think not, since nmap uses raw ethernet frames to get 
access to raw sockets there. I might be wrong though.

because you can't send a packet through ethernet
without knowing the target's MAC address unless you do a broadcast (am
I wrong?). Or do you populate your local ARP table manually or so?

You're not wrong, but the arp-cache is usually populated when it comes 
time to sending, so sending arp-requests again isn't usually required, 
although it would require that nmap reads the arp-cache of the system 
instead. I'm not sure that's available to userland on windows, but it 
might be. It would still have to send arp-requests for IP's not in the 
cache though.

Andreas Ericsson                   andreas.ericsson () op5 se
OP5 AB                             www.op5.se
Tel: +46 8-230225                  Fax: +46 8-230231

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