nmap questions

["Steven A. Fletcher" <sfletcher () integrityts com>]

I'm not sure if this is the right place to ask this or not, but I
thought I would give it a try.

I have run into an interesting problem when trying to UDP port scans
with nmap.  TCP SYN scans work fine, but if I try doing a UDP scan, it
comes back with "Too many drops ... increasing senddelay" numerous times
in a row.  It does seem that if I leave the scan running long enough, it
eventually completes the scan.  On a very small network, this is not a
problem.  However, on larger networks, I do not wish to wait that long.
Also, it happens on an internal network, so the problem does not appear
to be that the hosts are behind a firewall.

I have been trying to do what I can to have the scan finish in a fairly
reasonable amount of time, so I was hoping to improve the performance,
if possible.  A Google search returned nothing helpful, so that is why I
am trying here.

Just in case it is needed, here is the command line I am using:

                nmap -sS -sU -O -v -oA test -T3 -F --min_parallelism 100
192.168.1.0/24

Also, the machine is running MandrakeLinux 9.2 and kernel version
2.4.26.

Any help is greatly appreciated.

Steve Fletcher
Senior Network Engineer, MCSE, Master ASE, CCNA
Integrity Technology Solutions
Phone: (309)664-8129
Toll Free: (888) 764-8100 ext. 129
Fax: (309) 662-6421
sfletcher () integrityts com


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