Re: Question about negated and non-negated variables in rules

[Matt Kettler <mkettler () evi-inc com>]

At 08:49 AM 11/27/2003, J-H. Johansen wrote:
> I'm working on some ICMP rules and was wondering
> Recently I added a variable which contains our homenet with exclusions:
>
> var NOT_ICMP_SERVERS [$HOME_NET,!xxx.xxx.xx.xxx/32,!xxx.xx.xx.xx/32]
>
> This failed while running a check so I've also tried:
>
>
> Any clues as to how this must be done ?


All of the above rules are logically equivalent to "any".

what you really want is:

var NOT_ICMP_SERVERS ![$HOME_NET,xxx.xxx.xx.xxx/32,xxx.xx.xx.xx/32]


ie: Not (a or b or c) instead of (not a) or (not b) or (not c).


Work through the boolean math... c matches (not a) as well as (not b). Thus 
everything, including a, b and c, will match the second version.



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