[freebsd-questions] Deny large number of IPs via ipfw

[Howard Jones]

Dan Mahoney, System Admin wrote:
> Hey all,
>
> I've got a file that I just synced from a major RBL, and I'd like to 
> just use it to globally deny access to my system.  Is there an easy 
> way to do this within ipfw -- the file is about 3 *million* lines, and 
> is from cbl.abuseat.org.
I do similar things using IPFW2's tables:

table 1 flush
table 1 add firstip
table 1 add 3millionthip
deny tcp from table(1) to me 25

ipfw tables use the same lookup structure as the FreeBSD routing table, 
so it's got to be reasonably efficient. I've never used it with quite 
that many entries though!

Chances are, you can aggregate your address list to reduce it somewhat 
though.

Have fun,

Howie