Re: Simultaneous invocations of nmap

[doug () hcsw org]

Hi Rick,

Good question. Yes, people have thought about doing this before. In Fyodor's
soon-to-be-released book on Nmap there is a short section about executing
multiple instances in parallel. Fyodor warns that performance can actually
suffer due to context switching and memory overhead.

Usually one Nmap instance will be able to fully saturate your network
connection to the target networks, but this isn't to say that you shouldn't
give it a shot. If you do, please let us know how it turns out. In particular,
I'm curious as to whether this tactic could improve performance by taking
advantage of multiple processors/cores in modern SMP machines.

Good luck,

Doug


On Tue, Feb 19, 2008 at 08:29:30PM -0500 or thereabouts, Rick Rineholt wrote:
> Hi
> Has anyone done any performance studies on invoking simultaneous 
> instances of nmap on the same machine each covering separate subnets 
> versus executing a single instance specifying all the subnets?  One 
> reason I ask is I thought I read some info that nmap has some built in 
> mechanism to throttle back sending out explanatory packets if it starts 
> losing too many and surely having more than one instance at a time 
> running I would think would interfere with that mechanism. 
> Are there any guide lines available to help performance of discoveries 
> on very large networks?
> Thanks
>
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