mod evasive not working properly on ubuntu 10.04

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http://serverfault.com – I have an ubuntu 10.04 server where I installed mod_evasive using apt-get install libapache2-mod-evasive I already tried several configurations, the result stays the same. The blocking does work, but randomly. I tried with low limis and long blocking periods as well as short limits. The behaviour I expect is that I can request websites until either page or site limit is reached per given interval. After that I expect to be blocked until I did not make another request for as long as the block period. However the behaviour is that I can request sites and after a while I get random 403 block (HowTos)