VMware ESXi 4.1 Embedded and vCenter Server 4.1 Edition


ESXi Configuration Guide : Networking : Advanced Networking : VLAN Configuration

VLAN Configuration
Virtual LANs (VLANs) enable a single physical LAN segment to be further segmented so that groups of ports are isolated from one another as if they were on physically different segments.
Configuring ESXi with VLANs is recommended for the following reasons.
You can configure VLANs in ESXi using three methods: External Switch Tagging (EST), Virtual Switch Tagging (VST), and Virtual Guest Tagging (VGT).
With EST, all VLAN tagging of packets is performed on the physical switch. Host network adapters are connected to access ports on the physical switch. Port groups that are connected to the virtual switch must have their VLAN ID set to 0.
With VST, all VLAN tagging of packets is performed by the virtual switch before leaving the host. Host network adapters must be connected to trunk ports on the physical switch. Port groups that are connected to the virtual switch must have an appropriate VLAN ID specified.
With VGT, all VLAN tagging is performed by the virtual machine. VLAN tags are preserved between the virtual machine networking stack and external switch when frames are passed to and from virtual switches. Physical switch ports are set to trunk port.
Note
When using VGT, you must have an 802.1Q VLAN trunking driver installed on the virtual machine.