There are two generic types of port group as follows,

  1. Virtual machine – This port groups is for guest virtual machines.  
  2. VMkernel – This port groups are for ESXi management functions and storage.

Purpose of  VMkernel port group:

  • Management traffic – Carries the configuration and management communication for ESXi hosts, vCenter Server, and host-to-host High Availability traffic. By default, when you install the ESXi software, a vSphere Standard switch is created on the host together with a VMkernel adapter for management traffic. To provide redundancy, you can connect two or more physical NICs to a VMkernel adapter for management traffic.
  • vMotion traffic –  Accommodates vMotion. A VMkernel adapter for vMotion is required both on the source and the target hosts. The VMkernel adapters for vMotion should handle only the vMotion traffic. For better performance, you can configure multiple NIC vMotion. To have multi NIC vMotion, you can dedicate two or more port groups to the vMotion traffic, respectively every port group must have a vMotion VMkernel adapter associated with it. Then you can connect one or more physical NICs to every port group. In this way, multiple physical NICs are used for vMotion, which results in greater bandwidth. NOTE vMotion network traffic is not encrypted. You should provision secure private networks for use by vMotion only.
  • Provisioning traffic – Handles the data that is transferred for virtual machine cold migration, cloning, and snapshot creation.
  • IP storage traffic and discovery – Handles the connection for storage types that use standard TCP/IP networks and depend on the VMkernel networking. Such storage types are software iSCSI, depended hardware iSCSI, and NFS. If you have two or more physical NICs for iSCSI, you can configure iSCSI multipathing. ESXi hosts support only NFS version 3 over TCP/IP. To configure a software FCoE (Fibre Channel over Ethernet) adapter, you must have a dedicated VMkernel adapter. Software FCoE passes configuration information though the Data Center Bridging Exchange (DCBX) protocol by using the Cisco Discovery Protocol (CDP ) VMkernel module.
  • Fault Tolerance traffic – Handles the data that the primary fault tolerant virtual machine sends to the secondary fault tolerant virtual machine over the VMkernel networking layer. A separate VMkernel adapter for Fault Tolerance logging is required on every host that is part of a vSphere HA cluster.
  • vSphere Replication traffic – Handles the outgoing replication data that the source ESXi host transfers to the vSphere Replication server. Dedicate a VMkernel adapter on the source site to isolate the outgoing replication traffic.
  • vSphere Replication NFC traffic – Handles the incoming replication data on the target replication site.
  • Virtual SAN traffic – Every host that participates in a Virtual SAN cluster must have a VMkernel adapter to handle the Virtual SAN traffic.