Virtual Guest Tagging (VGT)

Virtual Guest Tagging (VGT)

  • You must install 8021.Q VLAN trunking driver instide virtual machine guest opearting system.
  • Only the e1000 vNIC can be used for Windows guestOS
  • All the VLAN tagging is performed by your virtual machine with use of trunking driver loaded/installed 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.
  • Need to configure a Virtual Machine with a VLAN ID 4095 to allow traffic.
  • The physical switch port connecting the uplink from the ESX should be configured as Trunk port.
  • If a Windows guest is configured for vmxnet or VLance, VGT is usually not possible 

 Advantages

  • Several VLANs on a single virtual NIC possible
  • Not limited to four VLANs per VM
Disadvantages
    • For troubleshooting network engineers and VM administrators have to be involved
    • ESX admin need to know the setup of the physical switch
    • Only the e1000 vNIC can be used for Windows guestOS
    • Need to use VLAN 4095 to allow traffic (covered later)

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