/etc/hosts.allow
/etc/hosts.deny
Access controls that should be enforced by tcp-wrappers are defined here.
Further details are described in hosts_access(5).

# /etc/hosts.allow
sshd: 1.2.3.0/255.255.255.0
sshd: 192.168.0.0/255.255.255.0

# /etc/hosts.deny
sshd: ALL

sudo ipfw add allow src-ip 10.0.0.0/8,172.16.0.0/16,192.168.0.0/16 dst-ip me dst-port 22
sudo ipfw add reject src-ip any dst-ip me dst-port 22