Strange problem with Asterisk, iptables + fail2ban

Hi all, I wonder if somebody can help with this?

I have Asterisk 11 installed and all running for quite some time. I have iptables and fail2ban set up too, and all configuration seems good. I’ve checked it a couple of times.

Everything works well together and all connections from outside work. Until the system is rebooted?

After a reboot all three services start up ok, but Asterisk will not accept connections. Nothing gets through. Then if I stop fail2ban, everything connects again. The strange thing is that if I then restart fail2ban (same settings) everything continues to work well together. It will work fine like that until another reboot and then I have the same problem.

I have tested it quite a few times to confirm. I am fairly new to Asterisk and any help would be greatly appreciated! Thank you.