Cluster#2 - Setting up an IPSec VPN into the Cluster

I want to set up the cluster to provide an IPSec VPN into the No-Mans Land vlan.  From there, I intend on setting up the other three RPis to connect to various vlans throughout my network.  The following diagram shows what I intend on doing:

The RPi coming from the Internet into NoManVlan would run the IPSec VPN.  I would then be able to access the cluster from external places.  The other three RPis would then perform the function of a gateway into other vlans from there.  Quagga would still be used to setup the routing tables in each RPi with respect to the NoManVlan.