Josh Brooks wrote:
Again, thank you very much for your advice and comments - they are very
well taken.

I will clarify and say that the fbsd system I am using / talking about is
a _dedicated_ firewall.  Only port 22 is open on it.

The problem is, I have a few hundred ipfw rules (there are over 200
machines behind this firewall) and so when a DDoS attack comes, every
packet has to traverse those hundreds of rules - and so even though the
firewall is doing nothing other than filtering packets, the cpu gets all
used up.
There is sorting that you can do, like putting the highest-traffic rules near the top. ipfw terminates the search on the first matching rule except for count and skipto. Also, the fewer items that have to be checked the faster the rule is. Perhaps there is some aggregation that can be done with the rules themselves?


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