WP fail2ban fully supports multisite networks in both the Free and Premium versions.

WP fail2ban is a “network-only” plugin; in other words, it can only be activated at the Network level rather than for each individual site. For the Premium version this has two important implications:

1. it requires at least a Silver license,
2. it requires only one license for the whole network

Site administrators can only see the Event Log entries for their site.