00:d0:b7:df:ee:4a 192.168.1.100 Third column is a comment 00:d0:b7:16:0b:f9 192.168.1.64 00:d0:b7:16:0b:f9 192.168.1.66 There can be more than one IP 00:00:21:e9:fe:9a 192.168.2.56 00:08:c7:eb:22:6c 192.168.2.56 Also more than one MAC 192.168.16.147 00:04:76:18:a0:b9 Order doesn't matter 00:00:00:00:00:00 192.168.50.163 Zero MAC == any MAC 00:0d:61:76:ef:eb 0.0.0.0 Zero IP == any IP 00:02:b3:60:50:9c 127.0.0.1 Known wrong IP == MAC blocked 00:0f:5b:83:30:0a host.domain.tld Hostnames resolved 00:00:00:00:00:00 192.168.4.0/24 Allow subnet de:ad:be:ef:12:34 192.168.0.0/16 Block all other subnets # 00:0c:6e:a0:f6:6d 192.168.1.254 Comment + Another comment