Vagrant - share host VPN with guest

So I have an interface for a VPN connection (jnc0), and also a vagrant guest which talks to my machine through another separate interface (vboxnet1). My host OS is OS X Mountain Lion, and the Vagrant (VM) guest OS is CentOS 6.3.

How can I set something up so that the CentOS guest will be able to talk to hosts on the other side of the VPN through my OS X host?

If you are using Virtualbox as your VM provider, I've successfully used this snippet to enable the use of a host VPN connection on a guest VM.

config.vm.provider :virtualbox do |vb|
    vb.customize ["modifyvm", :id, "--natdnshostresolver1", "on"]
end

You may have seen the following code snippet online which no longer works on newer versions of Vagrant:

Replaces the earlier config.vm.customize ["modifyvm", :id, "--natdnshostresolver1", "on"]