What is a Virtual Switch Used For?

  • By
  • June 19, 2019
  • VMware
What is a Virtual Switch Used For?

What is Virtual switch?

We all are aware of network device switch. Switch is used to connect different nodes in network.

It is responsible to communicate between devices connected to it. Switch operates on Layer 2 of OSI model and it works on MAC address.

In VMware ESXi, we can create virtual switch which connects different virtual machines, allow them to communicate with each other and also allow traffic to be sent out from esxi server in the network.

Hence we can also say that virtual switches connects virtual environment with physical one.

We cannot connect two virtual switches directly with each other.

Normally every virtual switch is connected to physical Network interface called as uplink.

A single virtual switch can have more than one uplink to provide redundancy. We can configure those

Uplinks for load balancing or Failover.

These uplinks (Physical Network Interface) are defined as vmnic0, vmnic1 ….switch 1

VMNIC- uplinks (Physical Network Interface) of ESXi host.

VNIC– Network interface of Virtual Machine.

VMK 0/1…- Virtual Machine Kernel Interface/Adapter

What is port Group?

Port group in simple language can be defined as network. We can assign VLAN ID for each port group.

Unlike every physical switch has   switch-ports, virtual switch has virtual ports which can be aggregated

Under port group.

There are two types of port groups namely –

  1. VMPG (Virtual Machine Port Group)

This type of port group provides connectivity to Virtual machines. We can also assign VLAN ID to the port group.

  • VMKPG (Virtual Machine Kernel Port Group)-We can add  Kernel adapter in VMKPG and assign IP address to the VMkernal Interface which is used to connect with the host.

Following services can be enabled on this adapter.

  • VMotion traffic- If enabled on TCP-IP network, carries VM migration traffic.
  • Provisioning Traffic-It allows data transferred for virtual machine eg. Cold Migration
  • Fault Tolerance Traffic- Fault Tolerance logging Traffic
  • Management Traffic-allows traffic between VCenter and Host.
  • Vsphere Replication Traffic- Traffic from ESXi Host to replication Server.
  • Vsphere Replication NFC Traffic- Incoming replication traffic on  target site
  • Virtual SAN Traffic-For every host which is part of VSAN, it has to be enabled.

Below image shows port groups structure.



Virtual Switch Types-

There are two types of virtual switches namely-

  1. Standard switch – This is basic switch that we can create at ESXi level. Standard switch can be created in all esxi editions.
  2. Distributed switch- This type of switch is created at vcenter level only.  It can also be deployed in the template mode on multiple esxi. They can be created only if we have Enterprise level Licensing.

It supports following features

  • Inbound and outbound traffic shaping
  • Load Based Teaming method is only supported by Distributed Switches.
  • VM port Blocking can be enabled so that data will not be send and received through it.
  • We can monitor the traffic passing through distributed switches using Netflow.
  • We can allow Private VLANs to be defined on distributed switch.

Load Balancing and Failover-

We can aggregate multiple uplinks as NIC team and configure them for load balancing (Active –Active) or failover (Active-Standby).

Load Balancing techniques used are –

  • Route based on originating Virtual Port
  • Route Based on IP Hash
  • Route Based on source MAC Hash
  • Route Based on physical NIC load

For Failover setting we can select below options for failover detection.

  • Link state Only – Failover only depends on link status. It will monitor things like disconnected cable or switch power failure.
  • Beacon Probing- Make use of beacon packets which are transmitted and received back through Uplinks to detect link failure. Beacon is sent every second. It detects upstream network failure which cannot be otherwise detected by Link State Only Method.

Some Maximum Values (ESXi Host Networking) that you should know-

  • Port Groups per standard switch- 512
  • Port Groups per Distributed Switch- 10000
  • Ports per distributed switch- 60,000
  • VSS Port Groups Per Host-1000



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