Level 1 - Server Level 1 - Workstation
The /etc/hosts.allow file specifies which IP addresses are permitted to connect to the host. It is intended to be used in conjunction with the /etc/hosts.deny file.
The /etc/hosts.allow file supports access control by IP and helps ensure that only authorized systems can connect to the system.
Run the following command and verify the contents of the /etc/hosts.allow file:
# cat /etc/hosts.allow
Run the following command to create /etc/hosts.allow:
# echo "ALL: <net>/<mask>, <net>/<mask>, ..." >/etc/hosts.allow
where each <net>/<mask> combination (for example, “192.168.1.0/255.255.255.0”) represents one network block in use by your organization that requires access to this system.
Contents of the /etc/hosts.allow file will vary depending on your network configuration.