Nmap Development: Re: Possible error message bug in nmap-4.11 on Gentoo

[Professor Messer <messer () spamarrest com>]

Remember also that if you're scanning a local subnet, the latest Nmap 
verisons won't perform an ICMP nor a TCP ACK on port 80. For all local 
subnet "pings" (including the Nmap ping process prior to a scan), nmap 
uses the much more efficient and effective ARP process to determine 
local device availability. Since an ARP isn't an IP frame, there 
shouldn't be a specification of ports when the local subnet is involved 
exclusively with an -sP option.

Perhaps a more refined error message would be in order, and an update to 
the man page.

--
James "Professor" Messer
Author, Secrets of Network Cartography: A Comprehensive Guide to Nmap
http://www.networkuptime.com/nmap

Andreas Ericsson wrote:
> Diman Todorov wrote:
>   
> > > Well, you *are* telling nmap to do a ping-scan (-sP) which doesn't use
> > > ports, but then you specify ports as well.
> > >       
> > This is not correct.
> > from the nmap man page:
> > <snip>
> >                The -sP option sends an ICMP echo request and a TCP  
> > packet to
> >                port 80 by default. When executed by an unprivileged  
> > user, a SYN
> >                packet is sent (using a connect() call) to port 80 on the
> > </snip>
> >
> > IMHO -sP should respect -p
> >
> >     
> Touché. I should rtfm more carefully or, as in this case, at all :-)
>
> I'm still not sure it makes sense though, unless you use the scan option 
> to control output (i.e. make hosts responding to any of the tcp-ports 
> given in the range show as "up", but nothing else). Oh well. I'm sure 
> it'll all turn out for the best.
>
>   

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