What are Virtual Switches and Standard Switches?

Introduction

In this article, you will learn about virtual switches and standard switches.

Virtual Switches

At the core of vSphere networking are virtual switches (vSwitches). They allow virtual machines to connect to each other and to connect to the outside world. By default, each ESXi host has a single virtual switch called vSwitch0.

The connection between a virtual machine and a virtual switch is similar to the connection between a computer's physical network adapter (NIC) and a physical switch. But instead of using a wired Ethernet cable, the virtual machine is connected to the port on the virtual switch by a virtual wire.

As with a physical switch, Layer 2 frames enter and exit a vSwitch. As with a physical switch, a vSwitch has ports organized into port groups. As with a physical switch, a vSwitch has uplink ports. These are physical network adapter ports found within the ESXi host, and connect the virtual switch within the ESXi host to a physical switch.

physical switch

Uplinks connect the virtual switch to the physical world: they move physical 0s and 1s off the host and out into the world. A virtual switch can have one or more uplinks. Just as you can connect the uplink ports between the two physical switches in the virtual world, you can connect or uplink a virtual switch to a physical switch.

vSwitches allow you to make adjustments to your Virtual Local Area Networks (VLANs), to some of your security settings, to your load balancing, and to your Maximum Transmission Units (MTUs), which relate to the size of data frames, as well as to other settings which are beyond the scope of this course.

Standard Switches

vSphere supports two types of virtual switches, the standard virtual switch (the vSwitch or VSS) and the distributed virtual switch (or VDS).

A standard switch works like a physical Ethernet switch. It detects which virtual machines are logically connected to each of its virtual ports and uses that information to forward traffic to the correct virtual machines. A standard switch can forward traffic internally between VMs within the same ESXi host, between VMs on different ESXi hosts, and between VMs and physical machines, and can link to external networks.

A vSphere standard switch consists of port groups, VMkernel adapters, and uplink ports. To provide network connectivity to hosts and virtual machines, you connect the physical NICs of the hosts to uplink ports on the standard switch. Virtual machines have network adapters (or vNICs) that you connect to port groups on the standard switch.

Every port group can use one or more physical NICs to handle its network traffic. If a port group does not have a physical NIC connected to it, VMs on the same port group can only communicate with each other and not with the external network.

To ensure efficient use of host resources on ESXi hosts, the number of ports of standard switches is dynamically scaled up and down. A standard switch on such a host can expand up to the maximum number of ports supported on the host.

A VMkernel adapter is a port that is used by the hypervisor to attach a service to the network. Every VMkernel adapter has an IP address by which this service is accessible.

The uses of this VMkernel adapter include.

VMware vMotion (which enables you to move VMs from one host to another while they're powered on with no downtime.
Management port (which is used for ESXi management traffic and in most cases except vSAN implementations- HA (or high availability) traffic)
IP storage (which is any form of storage that uses TCP/IP network communication as its foundation)
vSphere replication
vSAN data replication

vSphere standard switches are created and configured on a per-host basis. So, if you have three hosts, you’ll need three virtual networks, three virtual switches, and three supporting port groups. Each host can have up to 4096 ports across both standard and distributed switches; a maximum of 1016 of these ports can be active at one time. Each standard switch can have up to 512 port groups.

Each logical port on the standard switch is a member of a single port group. Each port group on a standard switch is identified by a network label, which must be unique among the other port groups on a host, but consistent across hosts in order to ensure network connectivity.

Virtual machine

Although by default vSwitch policies (security policies, for example) are automatically assigned to the vSwitch's port groups, port group policies can be configured manually.

vSphere network switches can be divided into two logical sections. The data plane carries out tasks such as packet switching, filtering (where a switch discards a frame that has the same source and destination MAC addresses), and tagging (where frames are tagged to indicate which VLAN they belong to). The management plane is where an administrator configures the functions of the data plane. Each vSphere standard switch contains both data and management planes, and the administrator configures and maintains each switch individually.

vSphere standard switches are supported by NSX-V, but not by NSX-T. Instead, VMware has developed a new virtual switch for the changing demands of modern networking.

The switch is called an N-VDS, and we will look at it in the next section.