I'm trying to use a virtual machine to bridge connections between the VirtualBox internal network and my host's network.
The purpose of this is to be able to firewall connections without having to configure the guests to use a specific gateway or proxy. This is part of some automated testing I'm doing.
My current setup looks like this:
{Internet} <=> Host <=VBox Bridged-eth0=> Bridge VM <=eth1-Internal Network=> Internal VM
Ubuntu 16.04 is the OS on the host and VMs.
Bridge VM has eth0 and eth1. These two interfaces are bridged with bridge-utils. The bridge works when I use NAT instead of Bridged networking. By this, I mean I can ping Google from the Internal VM when eth0 is NAT, but not when it is Bridged. In both modes I can get an IP with DHCP so (some?) broadcasts seem to work, but arp resolution does not (arp command returns empty after some time, route doesn't know the mac of the gateway).
Can anyone explain why this is happening? I'm assuming it's some limitation of the VirtualBox software network device? I'm hoping there's a way around this as I need to be able to access all the VMs from my host whilst still being able to block their connections with this Bridge VM as a transparent firewall.
Thank you.
