First of all I would stay away from vRouter, as in your situation you will most probably want to use VSLS, where you can use multiple cluster members and share the load across them. On the internet side you would use a vSwitch, as you most probably will use 1 VLAN to hook the different customers to the Internet?
On the internal side you will need to use a trunk with a VLAN per customer to your router and hook each VLAN into each customers' VRF.
At least that is how we do it. vSwitch is used whenever there is a need to use the same VLAN on more than one VS.
All other traffic, also DMZ's, are just connected via a VLAN directly to the VS.
To get back to the clustering, VSLS is Virtual System Load Sharing and allows you to define how the load will be shared, there are 3 options:
- automatic based on the weight you assign to each VS (default is 10)
- all on 1 box
- specific VS assigned to a physical box, so manual assignment
In all above options HA is still available, so when 1 box fails, the VS's will be moved over to the other member(s)
Next to that when you do have more than 2 members there are 3 states for each VS on each members, it can be
- active this is the member that is handling all traffic for that VS
- standby this is the member that is getting the state table updates and will take over when the active member fails
- backup. this is the member that is in cold standby, it will move to standby, if it is the only other member available or when it is the next in priority to become standby when the active fails.