Before you can test the connectivity between your devices, you need to take into account the following points:
Each IP address space works like a LAN network, that means that you can perform a connectivity test (PING) between your endpoints without using a VPN. Indeed, the endpoints are already inside the LAN.
Note: If you have more than 1022 devices, more than one IP address space will be required. Two devices which belong to two different IP address spaces will not be able to ping each other.