How to configure ESX for use with a Native VLAN

Issue:

Network traffic on the Native VLAN does not leave the virtual switch/port group.  Guest OS’s that are on the same virtual switch and port group configured for use with the Native VLAN may only communicate with each other.

 

All other Port Groups configured with VLAN IDS in ESX work correctly.

 

Cause:

The physical switch port(s) that is used as the uplink (trunk) to the virtual switch has a Native VLAN configured.  The VLAN ID specified as the Native VLAN is also configured as the VLAN ID in the affected Port Group.

 

Example:

Cisco Command

switchport trunk native vlan 45

 

ESX Port Group Configuration

 

Solution:

If you specify a Native VLAN on the physical port used as the uplink (trunk) to the virtual switch you should leave the VLAN ID blank when creating the associated port group for that VLAN.

 

As an alternative you may remove the Native VLAN configuration on the physical port used as the uplink (trunk) to the virtual switch.  This will allow the VLAN ID to properly pass to the virtual switch.

 

More Information:

The reason the VLAN ID in the Port Group configuration needs to be left blank is because the VLAN ID for the Native VLAN is not passed over the uplink (trunk) to the virtual switch.  Frames belonging to the Native VLAN do NOT carry the VLAN tags over switch ports configured with a Native VLAN.  Conversely, if an untagged frame is received on a switch port configured with a Native VLAN, the frame is associated with the Native VLAN for this port.

 

You can view VLAN IDs that are passed to (observed by) the ESX host by using the VI Client and going the Configuration tab of the ESX Host, and clicking Properties of the appropriate vSwitch.  On the vSwitch select the Network Adapters tab.  See the screen shot below for more information.

 

 

Uplink is the terminology that VMWare uses to explain the concept of connecting a Physical Switch to a Virtual Switch in their documentation and white papers.  A Trunk is the Cisco/Networking terminology and functionality that needs to be configured to allow VLAN tags to pass over a physical switch port.  An Uplink need not be a Trunk, unless VLAN tags need to be passed to the ESX Server.

 

VMWare ESX Server Network Configurations