I have been running fail2ban on my server for a while without any problems but have recently seen fail2ban restart randomly. After some looking in my logs I noticed that the restarts occur when ever someone gets banned.

So every time someone gets banned the fail2ban server restarts.

Here are a couple of logs.

    2012-03-23 00:58:39,025 fail2ban.actions: WARNING [dovecot] Ban xx.xx.xx.xx (ip removed)

What I have been able to find out is that the fail2ban bans the IP and then it restarts and the only error I can find is.

    2012-03-23 00:58:39,025 modprobe: FATAL: Module ip_tables not found.

Iptables is present and running - and I can issue any commands without iptables failing or fail2ban crashing.

Please let me know if you have any idea and if you would need the fail2ban config files

Edit:

I have been able to narrow it down to this iptables rule causing the errors:

    iptables -I INPUT -p tcp -m multiport --dports 110:995:143:993 -j fail2ban-Dovecot

Why would this multiport rule cause this error?

    2012-03-23 00:58:39,025 modprobe: FATAL: Module ip_tables not found.

System Information:

Centos 5.8
Fail2ban 0.8.2
Iptables 1.3.5