Network Segmentation Approaches

Scott Weeks surfer at mauigateway.com
Thu May 7 01:02:49 UTC 2015


On 07.05.2015 08:30, Scott Weeks wrote:
> --- rsk at gsp.org wrote:
> From: Rich Kulawiec <rsk at gsp.org>
>
> The first rule in every firewall is of course
> "deny all" and subsequent rulesets permit only
> the traffic that is necessary.
> ------------------------------------
>
>
> I think you got this backward?  That way all
> traffic is blocked, so none is allowed through.
> Also, deny by default at the end of the rule
> set is not the best thing for every network
> that needs a firewall.  Some just want to block
> bad stuff they see and allow everything else.
> (And some have stated here that they will block
> entire countries until their culture changes!)
---------------------------------------


--- aj at jonesy.com.au wrote:
From: Andrew Jones <aj at jonesy.com.au>

It depends on the software used and implementation.
Many rulesets for pf on BSD start with 'block in on 
interfaceX' for instance, because it uses a "last 
match wins" system, unless you use the 'quick' 
keyword to make rule processing stop if that rule
matches.
-----------------------------------------


I was assuming stop looking on first match.  So, 
"deny ip any any" blocks everything at the very 
beginning.

scott





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