For anyone interested; If you have supplemented your bad bots filter list, like I have, you most likely end up with thousands of banned IP's. In some cases even almost entire subnet ranges. Which you may (or may not) like to permanently ban.
For this purpose I've created a script that groups all bans from fail2ban into their respective subnets. Making it easier to see how many IP's from a subnet a currently banned. I shared the script in the Resource section of the forum, as I think this might help other users too. See: Instruction - [Fail2ban] Bash script to group multiple banned IP into subnets