Control plan communication occurs from the controllers to ESXi hosts for program elements of the DLR. You have the option to deploy a DLR with or without a DLR control VM. A control VM is deployed to facilitate features like dynamic routing. While the controllers distribute the routing information to the hosts, the controllers get the routing information from the DLR control VM as this is where peering between the DLR and other routers occurs. The controllers and the DLR control VM are all part of the control plane.
Note: a control VM for the DLR is not required, but you are limited to using static routes.
OK thanks. Do most people deploy a DLR control VM? Do I understand you correctly that you can't do dynamic routing on a DLR without a DLR control VM, even though you might have controllers working?
Are there any other factors that lead me to deploy or not deploy a DLR control VM?
As far as I've seen, most deploy a DLR control VM. Most reference architecture includes a DLR Control VM. Yes, a DLR control VM is required for dynamic routing protocols to be enabled on the DLR, as the control VM works in conjunction with the controllers. The ability to not deploy a DLR control VM is new as of 6.2. The Admin guide says the following on the matter:
Deploy Edge Appliance is selected by default. An edge appliance (also called a logical router virtual appliance) is required for dynamic routing and the logical router appliance's firewall, which applies to logical router pings, SSH access, and dynamic routing traffic.
You can deselect the edge appliance option if you require only static routes, and do not want to deploy an Edge appliance. You cannot add an Edge appliance to the logical router after the logical router has been created.
An NSX Edge (Edge Appliance) can be installed as an Edge Services Gateway or as a DLR. When you deploy an Edge, and select DLR, you are then asked if you want to deploy the DLR with or without an Edge Appliance...which in this case would be the DLR control VM.