Whitelisting is setup in the jail.conf file using a space separated list.
[DEFAULT] # "ignoreip" can be an IP address, a CIDR mask or a DNS host. Fail2ban will not # ban a host which matches an address in this list. Several addresses can be # defined using space separator. ignoreip = 127.0.0.1 192.168.1.0/24 126.96.36.199
# This will ignore connection coming from common private networks. # Note that local connections can come from other than just 127.0.0.1, so # this needs CIDR range too. ignoreip = 127.0.0.0/8 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16