Default Firewall Settings

The design of Photon OS emphasizes security. On the minimal and full versions of Photon OS, the default security policy turns on the firewall and drops packets from external interfaces and applications. As a result, you might need to add rules to iptables to permit forwarding, allow protocols like HTTP, and open ports. You must configure the firewall for your applications and requirements.

The default iptables on the full version have the following settings:

iptables --list
Chain INPUT (policy DROP)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere
ACCEPT     all  --  anywhere             anywhere             ctstate RELATED,ESTABLISHED
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:ssh

Chain FORWARD (policy DROP)
target     prot opt source               destination

Chain OUTPUT (policy DROP)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere

For more information on how to change the settings, see the man page for iptables.

Although the default iptables policy accepts SSH connections, the sshd configuration file on the full version of Photon OS is set to reject SSH connections. See Permitting Root Login with SSH.

If you are unable to ping a Photon OS machine, check the firewall rules. To verify if the rules allow connectivity for the port and protocol, change the iptables commands by using lsof commands to see the processes listening on ports:

lsof -i -P -n