Environment:

• Fail2Ban version : 1.0.2-2
• OS, including release name/version : Debian 12
• Fail2Ban installed via OS/distribution mechanisms
• You have not applied any additional foreign patches to the codebase
• Some customizations were done to the configuration

The issue:

The default config file has allowipv6 commented out, and fail2ban complains about it.

Steps to reproduce

Install from Debian repository and check systemd logs.

Expected behavior

No warnings

Observed behavior

An error is logged because allowipv6 is not defined in the config file.
WARNING 'allowipv6' not defined in 'Definition'. Using default one: 'auto'

Configuration, dump and another helpful excerpts

Default config from deb install

Relevant parts of journalctl -u fail2ban:

fail2ban-server[577104]: 2024-04-01 17:02:35,520 fail2ban.configreader   [577104]: WARNING 'allowipv6' not defined in 'Definition'. Using default one: 'auto'

The simple fix:

Uncomment line 62 in the default fail2ban.conf.