First of all, I'd like to draw more attention to what a VPN really is.
I am assuming that, by VPN, you mean something like this: OVPN - Free VPN Provider.
If this is not the case, please ignore everything I say.
First of all, how a VPN works is. VPNs are basically encrypted proxy servers.
A VPN client (after encrypting them, of course) forwards all of your data to the VPN server, where it is decrypted and the server executes the request. This request returns content, and that content is forwarded (after being encrypted) back to the VPN client, where you decrypt the return content and read it.
The problem I think I see is that your NAS device is on your Local Area Network (LAN). This means that the hostname (
mynas) is on your router's DNS.
This means that you can access the device by this hostname (
mynas), as long as you are asking the router for the IP of the NAS (all hostnames need to be converted into an IP address with a DNS in order for requests to happen).
Only the router knows where on Earth (or in this case the internet)
Your VPN server doesn't ask your router for DNS (that's normal).
Instead, it asks something like Google's DNS (
This means that it won't ask your router to access its DNS database.
The router is the only person (DNS) who knows where your NAS is locally. Google's DNS (that I've assumed your VPN server is using to fetch IPs) throws back an error at your VPN server, saying that it can't find
How to fix this problem
If you want to access your NAS by typing into your browser
ftp://mynas, you need to register the domain
mynas. I hate to break it to you, but that's not possible. There needs to be a suffix like
However, what you can do is you can register a public (instead of local) domain name (eg. mynas.com) so that any DNS (including Google's) will know where to find the NAS.
Yay! Everyone can find the IP of the NAS from anywhere (including the VPN server)!
Ways to solve this problem
You probably don't want to get a domain name just for your NAS (do you?), making that option invalid (but you could get one for free from Freenom)
FINAL ANSWER: You shouldn't use a VPN to access something on your local area network. There is no point in doing such a thing. The only reason to use a VPN while accessing your NAS on your own network is if:
* You want to hide your IP address from your own devices (are you logging yourself? Do you not trust yourself with your own privacy?) OR
* You want to demonstrate your trust to your VPN service provider
* You want more traffic to happen through the internet
As you can see, both these excuses are pretty lame :D. (What I am trying to say is don't use a VPN to access some device on your local network)