VLAN Tagging

VLAN tagging in ESX can be

• VST - Virtual Switch Tagging 
• EST - External Switch Tagging 
• VGT - Virtual Guest Tagging 

VST - Virtual Switch Tagging 

• VLAN tagging for all packets is performed by the Virtual Switch before leaving the ESX/ESXI host

• Port groups on the Virtual switch of ESX server should be configured with VLAN ID (1-4094).
  Note : VLAN ID 0 (zero) Disables VLAN tagging on port group (EST Mode)
  VLAN ID 4095 Enables trunking on port group (VGT Mode)
  
• Reduces the number of Physical nics on the ESX Host by running all the VLANs over one physical nic.
  
• The physical switch port connecting the uplink from the ESX should be configured as Trunk port And all the vlans defined in vSwitch need to be allowed.
  
• virtual machine network Packet is delivered to vSwitch and before it is sent to physical switch the packet is tagged with vlan id according to the port group membership of originating virtual machine.
  
• switch NIC teaming policy to Route based on originating virtual port ID (this is set by default)
  
• Physical  Switch Port Configuration :
  switch port need to be set to TRUNK mode
  dot1q encapsulation should be enabled. 

EST- External Switch Tagging 

• Esx host doesn't see the vlan tagging . vlan Tagging is done by Physical switch.
  
• No. of Physical Nics = No. of vlans
  
• Port groups on the Virtual switch of ESX server need not to be configured with the VLAN number or configure VLAN ID 0 (if it is not native VLAN
  
• Physical Switch Port configuration :
  Port need to be configured as access port.

VGT - Virtual Guest Tagging

• Install 8021.Q VLAN trunking driver inside virtual machine guest operating system.
  
•  All the VLAN tagging is performed by the virtual machine with use of trunking driver in the guest.VLAN tags are understandable only between the virtual machine and external switch when frames are passed to/from virtual switches.
  
• Virtual Switch will not be involved or aware of this operation. Vswitch only forwards the packets from Virtual machine to physical switch and will not perform any operation.
  
• Port group of the virtual machine should be configured with VLAN ID 4095
  
• Physical  Switch Port Configuration :
  switch port need to be set to TRUNK mode