Hello, in your opinion to share the network disk connected to the isb port of the router (asus dsl-68u), is it safer to use the asus ddns or a vpn? how do you configure the VPN to do this? what are the differences between VPN client and VPN server?
Vpn and ddns serve 2 completely different functions.
First, personally, I would never use the router as a file server. Ddns is simply a convenient way to access your network (by name instead of a potentially rotating IP address). Vpn provides security when accessing your network.
Ultimately, using both ddns *and* vpn is the easiest and most secure way to access your network remotely.
Re client vs server, pretty straight forward. You use a client app to connect to the VPN server to establish the secure link. Per your example scenario, you would setup the VPN server on your router and a client on your remote device.
You should start by reading some of the sticky threads here