This section provides a brief overview of the components of the DLR control and management planes.
The figure shows the components and the corresponding communication channels between them.
Has direct communications with the Controller Cluster
Has a direct permanent connection with the message bus client (vsfwd) process running on each host prepared for NSX
For each DLR instance, one Controller node (out of the available 3) is elected as master
The master function can move to a different Controller node, if the original Controller node fails
Each ESXi host runs two User World Agents (UWA): message bus client (vsfwd) and control plane agent (netcpa)
netcpa requires information from the NSX Manager to function (for example, where to find Controllers and how to authenticate to them); this information is accessed via the message bus connection provided by vsfwd
netcpa also communicates with the DLR kernel module to program it with the relevant information it receives from Controllers
For each DLR instance, there is a DLR Control VM, which is running on one of the ESXi hosts; the DLR Control VM has two communication channels:
VMCI channel to the NSX Manager via vsfwd, which is used for configuring the Control VM
VMCI channel to the DLR master Controller via netcpa, which is used to send the DLR’s routing table to the Controller
In cases where the DLR has a VLAN LIF, one of the participating ESXi hosts is nominated by the Controller as a designated instance (DI). The DLR kernel module on other ESXi hosts requests that the DI perform proxy ARP queries on the associated VLAN.