# comment line (a '#' as very first character)
#   a single IPv4 and IPv6 address
1.2.3.4
2001:0db8:85a3:08d3:1319:8a2e:0370:7344
#   address blocks in CIDR notation
127.0.0.0/8
10.11.128.0/17
192.168.0.0/24
#   hostnames
rome-fw.enterprise.com
hosts.friends.com