VMware NSX Device Communication

NSX Manager configures two user world agents on all hosts in a cluster:

  • Messaging bus UWA (vsfwd)
  • Control plane UWA (netcpa)

User world agents: netcpa (Control Plane Agent) & vsfwd (Message Bus Client)

Control Plane Agent (netcpa)

  • On NSX Data Centre for vSphere, control plane (netcpa) works as a local agent, communicating with NSX Managerand with the controller cluster.
  • Netcpa runs on each ESXi hosts prepared for NSX and it is responsible for sending the MAC address, IP information of each VM to NSX controllers.
  • Received information NSX manager through message bus agent, RabbitMQ server service is responsible running on manager.
  • Communication Channel Healthfeature is a health check which periodically reports the central control plane to local control plane status to NSX Manager.
  • This report also serves as a heartbeat to detect the operational status of the NSX Managerto ESXi host netcpa channel.
  • It provides error details during communication faults, generates an event when a channel goes into a wrong status, and also generates heartbeat messages from NSX Managerto hosts.
  • netcpacommunicates with the Message Bus Client (vsfwd) to retrieve control plane related information from NSX Manager.

Message Bus Client (vsfwd)

  • vsfwd service runs on each NSX prepared hosts and interacts with NSX manager to retrieve distributed firewall policy rules. Sends audit logs to NSX manager, received information from manager about creation/deletion of DLR, ESG.
  • A RabbitMQ message bus is leveraged for communication between the vsfwd (RabbitMQ client) and RabbitMQ server process hosted on the NSX manager.
  • The message bus is used by the NSX manager to send various information to the ESXi hosts, including policy rules that need to be programmed on the distributed firewall in the kernel.
  • The NSX Manager web application and NSX components on ESXi hosts communicate with each other through a RabbitMQ broker process that runs on the same virtual machine as the NSX Manager web application.

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