Added on Sep 13th, 2012 and marked as fail2ban security server

An IP-address that was blocked by fail2ban can be unblocked using the following method.

Get a list of all blocked addresses:

iptables -L -n

This will display all settings in the iptables firewall. For fail2ban there will be a section like this at the bottom:

Chain fail2ban-ssh (1 references)
target prot opt source destination
RETURN all --

The remove the IP <IP-ADDRESS> from the blockade:

iptables -D fail2ban-ssh -s <IP-ADDRESS> -j DROP

Source: Unblock IP from Fail2Ban