how many IPFW rules?

Dan Nelson dnelson at
Tue Oct 30 21:36:37 PDT 2007

In the last episode (Oct 30), eBoundHost: Artur said:
> Hello FreeBSD people!
> I have a smtp server under attack by what seems like a large botnet.  My 
> inetd is choking under the load and not allowing real mail through.  I've 
> successfully used tshark to find the offenders and put them into ipfw 
> firewall for port 25.
> So here is my question, I'm currently blocking 55,529 ip addresses and the 
> server seems pretty snappy, with no noticible load or lag.  How many more 
> rulesets will I be able to handle before things start getting fuzzy?

If you've created 55K separate rules and you're not seeing any
slowdown, then you must have a fast machine :)  Using an ipfw table
should be even better, though.  That lets you load any number of
ip/netmask pairs into a tree-based lookup table and match all addresses
using one ipfw rule.  The ipfw manpage has examples.

	Dan Nelson
	dnelson at

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