How to find IP of virtual machine?

If I have a VM (using VirtualBox, for instance) running inside my main OS; how can I identify the virtual interface and IP address (of the VM) from within the original (host) OS? I thought I could just use ifconfig, ip a, or similar; but no information related to the connected VM is displayed. Although it shows the main (host) OS has been assigned 192.168.1.104 via wlan0. However, if I run one of those commands from inside the VM, I can confirm that it's currently active @ 10.0.2.15 via eth0.