Virtual Switches

vSphere supports the use of virtual switches to manage network traffic to and from virtual machines.

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vCenter Server supports a distributed network model in which a distributed virtual switch manages ESXi host proxy switch configuration. In the distributed network model, a host proxy switch reflects the distributed virtual switch port settings, describes how physical network adapters are bridged to the switch, and performs network I/O.

■	On a standalone ESXi host, you can use a VMware standard virtual switch to support network traffic to and from virtual machines on the host.

To configure a vSphere network you perform the following operations:

■	Set up virtual switches

■	Define portgroups

■	Configure physical network adapters

Port Group

Port groups aggregate multiple ports under a common configuration. Each port can connect to a network adapter of a virtual machine, or an uplink adapter on the physical machine.

Each port group is identified by a network label, which is unique to the current host. Network labels make virtual machine configuration portable across hosts. All port groups in a datacenter that are physically connected to the same network (in the sense that each can receive broadcasts from the others) are given the same label. Conversely, if two port groups cannot receive broadcasts from each other, they have distinct labels.

You can use a VLAN ID to restrict port group traffic to a logical Ethernet segment within the physical network. For a port group to reach port groups located on other VLANs, the VLAN ID must be set to 4095. If you use VLAN IDs, you must change the port group labels and VLAN IDs together so that the labels properly represent connectivity.

Virtual Machine Network Interface

When you create a virtual machine, you include a VirtualMachineConfigSpec, which, in turn, includes a VirtualDeviceConfigSpec. The device property of VirtualDeviceConfigSpec is a VirtualDevice data object. One of the available virtual devices is VirtualEthernetCard. You can use one of the subtypes of VirtualEthernetCard to specify the virtual card to use and to specify the MAC address and whether wake-on-LAN is enabled for this virtual card. See Adding Devices to Virtual Machines. A limited number of adapters is supported. KB article 1001805 (http://kb.vmware.com/kb/1001805) discusses available network adapters and which adapter is appropriate in which situation.

VMkernel Network Interfaces

The network services that the VMkernel provides (iSCSI, NFS, and VMotion) use a TCP/IP stack in the VMkernel. This stack accesses various networks by attaching to one or more port groups on one or more virtual switches.

The VMware VMkernel TCP/IP networking stack handles iSCSI, NFS, and VMotion in the following ways.

■	iSCSI as a virtual machine datastore

■	iSCSI for the direct mounting of ISO files, which are presented as CD-ROMs to virtual machines

■	NFS as a virtual machine datastore

■	NFS for the direct mounting of ISO files, which are presented as CD-ROMs to virtual machines

■	Migration with VMotion

If you have two or more physical NICs for iSCSI, you can create multiple paths for the software iSCSI by using port binding. For more information on port binding, see the iSCSI SAN Configuration Guide.

A freshly installed ESX/ESXi system does not include VMkernel network interfaces. When you wish to migrate a virtual machine with VMotion, your VMkernel networking stack must be set up properly. When you want to use storage types that use TCP/IP network communications, such as iSCSI, you must provide a separate VMkernel network interface for that storage device. You must create any VMkernel ports you might need (see Adding a VMkernel Network Interface).

Physical Network Adapter (pnic)

The term pnic refers to the physical network adapters as seen by the primary operating system. When using the vSphere Web Services SDK, you can manipulate the adapter directly. When using the vSphere Client GUI, you manipulate instead the uplink adapter. On an ESXi host, each pnic has one associated uplink adapter.

In a vDS environment, you use a DVS uplink instead of an uplink adapter.