Sorry for my late.... 🙂
While connected via the mobile network, can you reach the vpn-server on it's vpn-address?
Yes I do reach the VPN-server.
it where internal addresses and they used RFC1918 addresses, all 10.0.0.0/8
Yes you are right. In Germany all providers use such IPs for the clients.
What do you mean by "I don’t reach my internal network"?
Can you successfully connect to the VPN server over the cellular network? Can you ping your VPN server? Can you ping any other hosts on your internal network?
And what address range is your internal network using? If its the same as the internal network of your mobile provider, youd have to work around this.
Yes I can successfully connect to the VPN server over the cellular network and I can ping the VPN-server and more hosts. And that sucks. I can ping the hosts but I can't access any webinterface. That's only when I'm connected over the cellular network.
I'm using 10.0.0.0/24 for my internal network. I don't know which subnetmask tmobile is using.