I assume you've named your Pi "ru0001" and have a local domain gmnnet?

What error do you get? Have you enabled the sshd server on the Pi?
VNC connects over port 5900 using a different protocol.

it is not clear where you're trying to connect from. Why are you expecting the gmnnet domain to exisst?

If you are trying to connect from your desktop to a Pi on your network then you don't need any domain, but your router must provide DNS resolution. Not all routers provide this.   My old BT router did, my new TPLink router doesn't, and so i can only connect with IP addresses.

If you're trying to connect from outside your network, then you will need to configure a VPN or NAT on your router. Thats not really a GMN question though, and there are other groups that could advise you better.

ah, right i did wonder if thats where it was coming from, but vas199228 was not very clear.

I don't think that provides SSH tunnelling though does it ? Only tunnels RTSP and VNC.

i appreciate english isn't your first language, but it would really help if you would provide more information about your problem. Error messages you get, what IP address you're using that works, why you are trying to use the VPN, that sort of thing.

As i mentioned earlier,  you need to describe the problem more clearly.

what are you trying to do, and what problems do you have?

Thanks for the additional information. 

Firstly, if it works with the ip address, whats the problem? Just use that :)

Secondly I assume you're trying to connect from an Ubuntu desktop to a remote pi, using the GMN VPN.  And the problem you have is that the hostname isn't resolved

You will probably find this google search useful. It was the first hit when i searched for "vpn ubuntu hostname not resolved"

https://askubuntu.com/questions/1417070/ubuntu-22-04-vpns-dns-server-not-used-for-resolving-addresses

As for why VNC works, its probably using netbios name resolution as a fallback. Netbios is a broadcast protocol from the windows world. Some routers broadcast netbios names for any DHCP allocations they've made and so if you were on Windows, the name resoultion would probably have worked. 

By the way i can strongly recommend google search as a quicker way to resolve problems with Linux, networking and the internet. While there are smart people in this group, its really not the best place to ask.