Fail2ban happily blacklisted a bunch of ipadresses (putting ip addresses from naughty hacking users as DROP lines in iptables). Here I describe the commands to remove these banned ip addresses. Execute them as user root or sudo.
List all current iptable rules:
#iptables -L -n --line-numbers [...] Chain fail2ban-APACHE (3 references) num target prot opt source destination 1 DROP all -- 192.168.2.23 0.0.0.0/0 2 RETURN all -- 0.0.0.0/0 0.0.0.0/0 [...]
Now you can remove that DROP line with this command (using the chain name and line number from above output):
#iptables -D fail2ban-APACHE 1
-D Delete matching rule from chain (fail2ban-APACHE in this case)
1 Rulenumber from chain