Re: variable nmap duration

[Fyodor <fyodor () insecure org>]

On Thu, Aug 31, 2006 at 03:43:11PM +0200, Daniel Rozsnyó wrote:
> Hello,
>
>   I am working on a FTP indexing service for our local college network.
> The on/off line hosts and available servers are discovered by stealth
> scan to port 21, per building subnet (4C, x10 buildings) which runs
> again and again. Exact command:
>
> /usr/local/bin/nmap -sS -P0 -p $tcpPort -n -T Normal -iL ./nmap.in -oX -
>
>   The problem is, that sometimes the scan runs for relatively long time,
> like 50 to 400 (sometimes over 1000) seconds. In 98%, it takes only 3 to
> 7 seconds (to scan the 4C). The distribution of long runs is totally
> random during the whole day and during the summer holiday the server
> mostly idles, so I see no reason for such a lags..

Using -T4 would likely help.  You may also get good results for
tweaking the other timing parameters described at
http://insecure.org/nmap/man/man-performance.html .

Cheers,
-F

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