Networking

Before we go for understaning vNetwork and vSwitch, let us understand the importance of vmware ESX/ESXi Network. The networking feature in the ESX/ESXi host allow virtual machines to communicate with each other as well as VMs on other host, IP based storage and physical machines. This means it is as good as configuring a physical network but the difference is that we don't have to deal with lots of networking cables. If the network is not configured properly it become difficult to manage VMs, IP storage etc.

In VMware ESX/ESXi network there are two important components to be understood; 1) vNetwork and 2) vSwitch.

Virtual Network provides networking for VMWare ESX/ESXi hosts and VMs. The fundamental component of a vNetwork is vSwitch.

Virtual Switch

-It directs network traffic between virtual machines and links to external networks. All network communications handled by a host passes through one or more virtual switches. A virtual switch provides connections for virtual machines to communicate with one another, whether they are on the same host or on a different host. A virtual switch allows connections for the management network on ESXi hosts and for the service console on the ESX host.

-We use vSwitch to combine the bandwidth of multiple network adapters and balances traffic among them. It can also handle physical network interface card (NIC) failover.

-Models a physical Ethernet switch e.g. VM's NIC can connet to a port and each uplink adapter uses one port.

-Virtual switches work at layer 2 of the OSI model. You can't have two virtual switches mapped to the same NIC but you can have two or more NICs mapped to the same virtual switch.

-When two or more virtual machines are connected to the same virtual switch, network traffic among them is routed locally. If an uplink adapter is attached to the virtual switch, eacj VM can access the external network that the adapter is connected to.

Let us now understand virtual switch in more details for ESXi hosts only.

Uplink Ports: Its number of Physical adapters (NIC) available.

Port Groups: A vSwitch can be subdivided into smaller units called port groups. There are three typs of port groups and each port group is related to different type of traffic: a) Virtual machines Port Group; b)Service Console port group (only ESX); c)VMKernel port group (used for vMotion, FT, IP Storage etc.)

A virtual switch provides three types of conection types to hosts and VMs.

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  Connecting VMs to the phycial netork.


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  Connecting VMkernel to physical network. VMkernel services include aces to IP storage, such as NFS or iSCSI, vMotion, access to the managment network on ESXi host.


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  Providing networking for the service console for ESX only.

Separate IP stacks are configured for each VMkernel port and the ESXi management netork port . Each ESXi management network port and each VMkernel port must be configured with tis own IP address, netwmask and gateway. All three port groups connect to outside world through physical adaptors assigned to the vSwitch. We can place all networks on a single vSwitch or multiple vSwitches can be opted which depends upon the situation.

There are two types of vSwitches; vNetwork Standard switch and vNetwork distributed switch. The vNetwork standard switch is configured at host level. We can have maximum of 4088 vSwitch ports per standard switch and 4096 vSwitch ports per host. The vNetwork distribued switch is configured at vCenter. Its components are same as vNetwork Standard switch but it functions as a single virtual switch across all associated hosts. This allows virtual machines to maintain consistent network configuration as the migrate across multiple hosts.

The virtual switches will be discussed in more details in succeeding posts.