I'm using a few VMs in virtual box that runs Debian OS. I have already created a network where the first VM acts as a gateway for the second VM to get the internet connection and the second VM acts as a gateway for the third VM so that it can essentially get internet access by going back to VM1. The problem is that I need to allow the first and third VMs to have an internet connection while forbidding the middle VM to have a connection to the internet. The first VM and the third VM should both be able to ping each other. How can I achieve this?