RE: Discovery Scanning Issues

["Lyal Collins" <lyal.collins () key2it com au>]

Ps.
The -T Polite setting just seems essential to ensure all ports and actually
tested - has anyone else noticed this?

Again, my experience is that even on Suse9.3 and a 100MBits LAN, nmap
exhausts the ip_conntrack pool (~49,000) although the machine has 768Mb of
RAM.
This ip_conntrack issue seems to pop up lots of places, just not noticed so
much on LAN-style environments



Lyal

-----Original Message-----
From: kataka () hush com [mailto:kataka () hush com] 
Sent: Sunday, 8 January 2006 2:48 AM
To: pen-test () securityfocus com
Subject: DSL: Discovery Scanning Issues


DSL was finally brought to where I live, and I have started 
experimenting with discovery scans using Nmap. 

The problem is, if I try and scan for more than 1024 ports on a 
single host, my cheep-o Zoom DSL router/modem/switch/thingy starts 
to flake out, in the sense I can't ping my DSL router any more and 
I loose connectivity to the Internet until I reset the router. 

I believe this is because Nmap is filling up my router's NAT pool 
or something. I've looked at the config of the router and it's only 
got a 1024 connection NAPT port limit that cannot be adjusted and 
timeouts measured in seconds as opposed to ms.

What should I do? Are other people with low-end DSL routers able to 
overcome this problem? Should I look at getting a better router, if 
so, what kind? Or, is it best to not scan through NAT and assign my 
Internet Routable IP to my scanning box directly? If so, how would 
this work under DSL, would I need to buy some kind of an Ethernet 
to RJ-11 adapter card, configure routing, install PPP encapsulation 
software on the box itself? 




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