mailing list archives
Re: massping issue
From: David Fifield <david () bamsoftware com>
Date: Thu, 2 Apr 2009 13:39:31 -0600
On Thu, Apr 02, 2009 at 09:06:50AM -0400, Justin Azoff wrote:
Hi, since upgrading from debian etch nmap to debian lenny nmap (4.11 to
4.62) I noticed that a script that runs a ping scan across our /16
stopped finding 90% of the hosts.
The command ran is simply:
nmap --host_timeout 2000 -n -sP -PE a.b.0.0/16
The highest latency on the network is under 100ms, so 2000 should be
more than high enough to find everything.
I used git bisect against git://git.debian.org/~lamont/nmap.git to track
this down to a commit, and the result was
which corresponds to '4.22SOC6'
The changelog for that says:
+o Included David's major massping migration project. The same
+ underlying engine is now uses for ping scanning as for port
+ scanning. We hope this will lead to better performance and
+ accuracy, as well as helping to de-bloat Nmap. Please test it out
+ and report your results to nmap-dev! For more details, see
the test I ran was:
time sudo nmap --host_timeout 2000 -n -sP -PE a.b.0.0/16 -oG - | grep
'Status: Up' -c
I verified that with the previous rev
(f501df2e2a74f0bc8ce35a9ddc67d6864afddf96) the results are:
with d37f15389455ff474c00223cbf18be4117cedd76 the results are:
so it runs in 1/10th the time, but finds 1/10th the hosts.
I also tested this with nmap-4.85BETA7:
and svn HEAD:
Thanks for your detailed report. I don't think --host-timeout is what
you want here. You want --max-rtt-timeout instead. --host-timeout is an
absolute start-to-finish limit on total time taken for each host.
Because 4096 hosts are scanned in parallel during ping scan, you are
only allowing 2 seconds to scan all 4096 of them.
The reason you got more hosts with 4.11 is that massping didn't respect
--host-timeout in that version. The option simply didn't have an effect
during ping scans. Now host are allowed to time out during ping scans,
and two seconds
So try using --max-rtt-timeout instead. Host timeouts are usually
specified in at least minutes, and RTT timeouts are usually in
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- massping issue Justin Azoff (Apr 02)
- Re: massping issue David Fifield (Apr 02)