Technical Best Practices

VMware Virtual Switch

vSphere Virtual Networking

vSphere virtual networking provides several services to the vSphere host and virtual machines. There are four types of network services enabled in vSphere networking:

1) Connecting virtual machines to each other within a single vSphere host
2) Connecting virtual machines to the physical network
3) Connecting VMkernel services (such as NFS, iSCSI, or vSphere vMotion) to the physical network
4) Networking for the management interface, which runs management services for vSphere hosts (set up by default during installation)

vSphere networking consists of two logical building blocks: Virtual Ethernet Adapters and Virtual Switches.

Virtual Ethernet Adapters

A virtual machine can be configured with one or more virtual Ethernet adapters. Virtual Ethernet adapters are presented to the guest OS by the virtual machine hardware. These virtual adapters are seen by the guest OS as common network interface cards and will use standard drivers available for the OS. There are also several special purpose virtual Ethernet adapters available that provide optimized performance in a virtual machine environment, with corresponding OS drivers provided as a part of VMtools. See the complete list of virtual Ethernet adapters supported by vSphere.

Virtual Switches

Virtual switches allow virtual machines on the same vSphere host to communicate with each other using the same protocols used with physical switches. The virtual switch emulates a traditional physical Ethernet network switch to the extent that it forwards frames at the data link layer. A vSphere host may contain multiple virtual switches, each providing more than 1,000 internal virtual ports for virtual machine use.

vSphere supports two kinds of virtual switches:

1) vSphere Standard Switch – A virtual switch configuration at the host level.

2) vSphere Distributed Switch – A single virtual switch that spans across all associated hosts. This approach allows virtual machines to maintain consistent network configuration as they migrate across multiple hosts. This switch has similar components to a standard switch and is configured at the vCenter Server level.

The virtual switch connects to the enterprise network through outbound Ethernet adapters.A maximum of 24 1GbE ports or 8 10GbE ports can be used for external connectivity. The virtual switch is capable of binding multiple VMNICs together, in a manner much like NIC teaming on a traditional server, offering greater availability and bandwidth to the virtual machines.

The following are important features of virtual switches:

Virtual ports: The ports on a virtual switch provide logical connection points among virtual devices and between virtual and physical devices. Each virtual switch can have up to 1,016 virtual ports, with a limit of 4,096 ports on all virtual switches per host. The virtual ports provide a rich control channel for communication with the virtual Ethernet adapters attached to them.

Uplink ports: Uplink ports provide the logical connectivity between the virtual switch and the physical adapters installed in the host. Uplink ports are connected to specific physical adapters based on configuration.

Port groups: Port groups make it possible to specify that a given virtual machine should have a particular type of connectivity on every host. They contain enough configuration information to provide persistent and consistent network access for virtual Ethernet adapters. Some of the information contained in a port group includes the virtual switch name, VLAN IDs and policies for tagging and filtering, the teaming policy and traffic shaping parameters

Uplinks: Uplinks are the physical Ethernet adapters that serve as bridges between the virtual and physical network. A host may have up to 32 uplinks.

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