firewall processing

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Jun 6th, 2008
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Hi all, if I created a rule on my firewall to allow any to any comms for all ip, would this have to look into every packet? and if I created a rule with a certain tcp port only allowed, which this mean less processing or more than the allow all rule ?

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Wantser1981_2 Mon, 06/09/2008 - 05:12
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If you have a firewall rule base applied to an interface, the packets are passed through the list from top to bottom, until an arguement is matched, be it allow or deny. If all arguements do not match then then unless you specifically allow a connection, it will be dropped by default.

So it doesnt matter whether you have one rule or 20 rules, all will be looked at until there is a match. The more rules you have the more processing needs to take place, but this is where you get into writing your policy to have the most popualr rules at the top.


carl_townshend Mon, 06/09/2008 - 06:28
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the firewall expert at my company says that if we have a rule that allows all ports from one ip to another ip will cause the firewall to have to look into each and every packet? I thought if there was an an allow all rule between ip's there would be less work to do?


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