First of all you do not need to burn an ISO Image to optical media to install it into a VM as it can be installed directly from ISO Image.
Secondly for testing purpose you do not need to actually install an OS, just use a Linux Live OS ISO Image like Tiny Core Linux to test with. The images are small, 12 MB for TinyCore.
Create two Other Linux VM's, not using Easy Install, and just assign the ISO Image to both and boot both VM's. Then in a Terminal ifconfig to get each IP Address and then ping each other IP Address. If this works, it tells us the expected default networking performs as intended.
This is done to ensure the expected default networking works as intended so as to focus troubleshooting in User Modified Settings that were probably not done properly however it's senseless to start a diagnostic/troubleshooting process unless one confirms the defaults work as intended! 