There are sites that check the open ports. Now I have a synology diskstation attached to my router/modem. It is the storage server of my LAN. Supposing that this checking finds ports 21 and 22 open. For ultimate security is it necessary to close these ports and how do we do that using your personal firewall. These ports can be opened or closed for inbound and outbound traffic. What if I wish to use port 21 for some ftp traffic. Shall I be rejected because the port is closed? Another point the router/modem supports portforwarding not only for IP4 but also for IP6 protocol through tunneling. There it uses randomly chosen port numbers which can not practically be controlled by human specified firewall rules. Does this pose a threat to the diskstation. Responses are welcome.