virtualbox.org

I use an ipsec cisco VPN connection to connect my Mountain Lion machine to a corporate network. I have an Ubuntu VM from which I would also like to access servers available only over the VPN. I have a bridged connection between Mountain Lion and the Ubuntu guest - thats how I usually use the VM as a development environment. i can ping the target server from OSX but not from the Guest VM. Is what I want to do even possible and, if so, how?

Other things I have tried:

Bridging using p2p0 as the adapter (the VM won't boot as it can't configure a network connection )

Is what I want to do even possible

Probably not. VPN sets up a tunnel to keep this from happening, and what the purpose was for VPN. You may be able to work around that but not easily, and has nothing to do with VirtualBox.

If you have a bridged connection you can probably install the VPN client software in the guest and make a VPN connection directly to your corporate server. I would be very surprised if you can find a way to share the host's connection. As Perry said, VPN connections are designed to be solely client to server connections. To have a shareable VPN link you need to set up a site to site (also called LAN to LAN or router to router) VPN connection.