You can edit Layer 2 security policies, such as MAC address changes and forged transmits, for a vSphere standard switch.

Layer 2 is the data link layer. The three elements of the Layer 2 Security policy are promiscuous mode, MAC address changes, and forged transmits. In non-promiscuous mode, a guest adapter listens to traffic only on its own MAC address. In promiscuous mode, it can listen to all the packets. By default, guest adapters are set to non-promiscuous mode.

You can override the switch-level settings for individual standard port groups by editing the settings for the port group.

For more information about security, see the vSphere Security documentation.


Launch the vSphere Client and log in to a vCenter Server system.


  1. Log in to the vSphere Client and select a host in the inventory pane.
  2. Click the Configuration tab and click Networking.
  3. Click Properties for the standard switch whose Layer 2 Security policy you want to edit.
  4. In the Properties dialog box for the standard switch, click the Ports tab.
  5. Select the standard switch item and click Edit.
  6. Click the Security tab.
  7. In the Policy Exceptions pane, select whether to reject or accept the Layer 2 Security policy exceptions.
    Option Description
    Promiscuous Mode
    • Reject — Placing a guest adapter in promiscuous mode has no effect on which frames are received by the adapter.
    • Accept — Placing a guest adapter in promiscuous mode causes it to detect all frames passed on the vSphere standard switch that are allowed under the VLAN policy for the port group that the adapter is connected to.
    MAC Address Changes
    • Reject — If you set the MAC Address Changes to Reject and the guest operating system changes the MAC address of the adapter to anything other than what is in the .vmx configuration file, all inbound frames are dropped.

      If the Guest OS changes the MAC address back to match the MAC address in the .vmx configuration file, inbound frames are passed again.

    • Accept — Changing the MAC address from the Guest OS has the intended effect: frames to the new MAC address are received.
    Forged Transmits
    • Reject — Any outbound frame with a source MAC address that is different from the one currently set on the adapter are dropped.
    • Accept — No filtering is performed and all outbound frames are passed.
  8. Click OK.