Filtering question: checking for many addresses in a single rule?

[Jos Backus]

If one has many (thousands) hosts/addresses that the same filter action needs
to be taken for, what would be the most efficient way to implement this using,
say, ipfw or ipfilter? I'm referring to the ability to create/load a large
hashed set of addresses and a way to refer to the set in a filter rule. So
rather than having many rules that need to be scanned sequentially there would
only be one rule and the matching mechanism would use a hash table instead.

Thoughts?

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Jos Backus                       _/  _/_/_/      Sunnyvale, CA
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jos at catnook.com        _/_/   _/_/_/          require 'std/disclaimer'