Re: How NAT reacts on table flood ?

[Lynx <lynx () enemy org>]

On Jul 11, 2006 at 1515 +0200, Norbert François appeared and said:
> Salut,
>
> I was wondering how the NAT reacts when its translation table is
> full... For example, suppose that you've 100 computers behind a NAT
> (University) and one (or more) of them engages purposely  a lot of
> connexion, in order to fill the NAT table, what will occur ?

That depends on your NAT implementation. I know from firsthand scanning
experience that a Linux router with stateful NAT tracking (i.e.
Netfilter-based) can be flooded (tested on 2.4.x and 2.6.x). After the
NAT table is filled the kernel has to wait for the state table entries
to timeout. There is an alternative way of doing NAT via the Linux
routing code. Unfortunately I don't know how this method performs.

Best,
Lynx.

-- 
FAITH, n. - Belief without evidence in what is told by one who speaks
            without knowledge, of things without parallel.
 -- http://www.alcyone.com/max/lit/devils/f.html --


------------------------------------------------------------------------------
This List Sponsored by: Cenzic

Concerned about Web Application Security? 
Why not go with the #1 solution - Cenzic, the only one to win the Analyst's 
Choice Award from eWeek. As attacks through web applications continue to rise, 
you need to proactively protect your applications from hackers. Cenzic has the 
most comprehensive solutions to meet your application security penetration 
testing and vulnerability management needs. You have an option to go with a 
managed service (Cenzic ClickToSecure) or an enterprise software 
(Cenzic Hailstorm). Download FREE whitepaper on how a managed service can 
help you: http://www.cenzic.com/news_events/wpappsec.php 
And, now for a limited time we can do a FREE audit for you to confirm your 
results from other product. Contact us at request () cenzic com for details.
------------------------------------------------------------------------------