VCAP5-DCA Objective 2.2 – Configure and maintain VLANs, PVLANs and VLAN settings


  • Determine use cases for and configure VLAN Trunking
  • Determine use cases for and configure PVLANs
  • Use command line tools to troubleshoot and identify VLAN configurations

Determine use cases for and configure VLAN Trunking

Updated: 14-09-2012

Official Documentation:
vSphere Networking, Chapter 7 “Advanced Networking”, Section, “VLAN Configuration”, page 68.

On a vSS you can only configure one VLAN ID per Portgroup.

A vDS allows you to configure a range of VLAN IDs per portgroup. In fact there are four options for VLAN type on a vDS:

  1. None
    VLAN tagging will not be performed by this dvPort group
  2. VLAN
    Enter in a valid VLAN ID (1-4094).  The dvPort group will perform VLAN tagging using this VLAN ID
  3. VLAN Trunking
    Enter a range of VLANs you want to be trunked
  4. Private VLAN
    Select a private VLAN you want to use – the Private VLAN must be configured first under the dvSwitch settings prior to this option being configurable

Now you can join physical VLANs to virtual networks.

Remember these VLAN IDs:
VLAN 0 = None;
VLAN 1-4094 = Valid IDs;
VLAN 4095 = All IDs.

Ingress= vDS incoming traffic
Egress = vDS outgoing traffic

Configure VLAN trunking

By default a dvUplink Group is configured for all VLAN IDs.

Figure 1

And on the dvPortGroup Level, you can define the desired ranges of VLAN IDs.

Figure 2

There is an Override on the Port Level!

Figure 3

Why create a VLAN trunk?

Configuring a VLAN trunk is useful for VLAN troubleshooting. This way the network traffic is delivered with a VLAN tag in the guest OS.
You have to configure your VM with a VMXNET3 or E1000 vmnic. Inside the guest OS, configure the VLAN advanced parameter and specify a VLAN ID.

Other references:

  • VMware KB 1003806 VLAN Configuration on Virtual Switch, Physical Switch, and Virtual Machines. Also info on External Switch Tagging (EST), Virtual Switch Tagging (VST), Virtual Guest Tagging (VGT)

Determine use cases for and configure PVLANs

Official Documentation:
vSphere Networking, Chapter 3 “Setting up Networking with vSphere Distributed Switches”, Section “Private VLANs”, page 27.

Private VLANs are used to solve VLAN ID limitations and waste of IP addresses for certain network setups.

A private VLAN is identified by its primary VLAN ID. A primary VLAN ID can have multiple secondary VLAN IDs associated with it.

  • Primary VLANs are Promiscuous, so that ports on a private VLAN can communicate with ports configured as the primary VLAN.
  • Ports on a secondary VLAN can be either:
    • Isolated, communicating only with promiscuous ports, or
    • Community, communicating with both promiscuous ports and other ports on the same secondary VLAN.

To use private VLANs between a host and the rest of the physical network, the physical switch connected to the host needs to be private VLAN-capable and configured with the VLAN IDs being used by ESXi for the private VLAN functionality. For physical switches using dynamic MAC+VLAN ID based learning, all corresponding private VLAN IDs must be first entered into the switch’s VLAN database.

A graphic will clarify this.

Figure 4 Origin:

Configuring pVLANs
In the VMware documentation, you can find the whole process, step-by-step.
However, if you are new to this subject, I recommend that you watch Eric Sloof’s tutorial on this subject.
An old proverb says: “An excellent video tells you more than 1000 written words”.

Figure 5 – Configuration of the pVLAN in Figure 4

Other references:

  • Excellent Tutorial on this subject is Eric Sloof’s video on Configuring Private VLANs.

Use command line tools to troubleshoot and identify VLAN configurations

Official Documentation:
The vSphere Networking Guide or even the vSphere Troubleshooting guide do not provide much information on this subject

Using command line tools to troubleshoot VLAN issues, there are a few options. Apart from which CLI (vSphere CLI, PowerCLI) and location (Local on a ESXi host, vMA or your desktop), these examples assume we are able to logon to an ESXI host:

Troubleshooting means in the first place, gathering information.

  • The /esx/vmware/esx.conf contains a section on network settings. Look for entries starting with: /net
  • The esx-vswitch –l command gives an overview of all vSS an dVS, including VLAN settings
  • The ESXCLI command does the same. For standard switches use:
    esxcli network vswitch standard portgroup list
  • The esxtop command in network display is always useful to collect network statistics.

For adjusting VLAN settings on a portgroup, use the esxcfg-vswitch command with the parameter  -v.

Other references:

  • VMware KB 1004074 Sample configuration of virtual switch VLAN tagging (VST Mode) and discusses the configuration of virtual and physical switches.

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