1. Create a new namespace:
   sudo ip netns add openvpn_namespace sudo ip netns
2. Attach whatever interface you want to this namespace (eg in this case tun0):
   sudo ip link set tun0 netns openvpn_namespace
sudo ip netns exec openvpn_namespace ip link set tun0 up
sudo ip netns exec openvpn_namespace ip link
sudo ip netns exec openvpn_namespace ip addr
3. Now need to manually assign your IP address to the linked namespace (eg below 10.8.0.2 on tun0 is assigned when connected to the VPN):
   sudo ip netns exec openvpn_namespace ip addr add 10.8.0.2/24 dev tun0
sudo ip netns exec openvpn_namespace ip addr
4. After that add the routing information manually (example below 10.200.23.0/24 is routed through 10.8.0.1):
   sudo ip netns exec openvpn_namespace ip route
sudo ip netns exec openvpn_namespace ip route add 10.200.23.0/24 via 10.8.0.1 dev tun0
sudo ip netns exec openvpn_namespace ip route
5. When executing command (for example connect to RDP just use the namespace):
   sudo ip netns exec openvpn_namespace xfreerdp /u:Mbouctroupeau /d:. /p:aisle-armament-PUDDLE /v:10.200.0.192