Re: faster scans? (nmap)

["Michael Starr" <mstarr () ampeisch com>]

If all you're looking for is which hosts are up, you could try using 
hping instead of nmap to do the initial scan -- then you could scan 
only hosts that you know are there with Nmap.  I believe that hping 
(haven't used it for a while, so check me on this) has an option to 
use protocols other than icmp, so it can detect hosts that drop echo-
request packets.  I've used hping in conjunction with nmap with 
pretty fair success.  The other thing that I've done from time to time 
is write Perl code, or batch scripts that will cycle through the ip 
ranges as an array, hash, or read directly from a file -- using Perl's 
system() function works pretty well with this.  It might or might not 
make things faster, but at least you don't have to manually run the 
scans, and you can do something else while they're running, and 
increase efficiency if not speed.

Hope it helps,
M.

On 1 Jun 2002 at 14:36, wirepair wrote:

lo all.
I'm sure most of you at some point in time need to scan 
class c after class c for hosts responding (most likely 
using nmap). Here's the issue, multiple class C's, must 
scan every ip with the -P0 option. Doing some testing with 
various flags to decrease the timing and still have the 
results be reliable. 1-1000 ports takes about 1293 
seconds... x 65.5 x 254 == hella long time. I'm doing 
vanilla tcp connect scans (Syns aren't reliable in this 
case), so I was wondering if any of you have any tips on 
speeding up the process and not loosing reliablity. Here's 
the actual syntax nmap -sT -v -n -P0 -p 1- ip.ip.ip.ip-ip. 
I've tried setting the amount of sockets to use to 100 and 
that increased it from 1293 to 588seconds. Still there's 
gotta be a better way. The reason they take this long is 
because there is no host at the ips i'm trying to scan, 
but still this is discovery and every ip needs to be 
scanned. Maybe changing timeouts in /proc/sys ? I'm 
running out of ideas any suggestions would be helpful 
(there really isn't much out there in the way of 
increasing timing on scans) Hell maybe i should be using a 
different scanner? Thanks,
wire
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