Information
Ensure that the MAC Address Change policy within the vSwitch is set to reject.
*Rationale*
If the virtual machine operating system changes the MAC address, it can send frames with
an impersonated source MAC address at any time. This allows it to stage malicious attacks
on the devices in a network by impersonating a network adaptor authorized by the
receiving network. This will prevent VMs from changing their effective MAC address. It will
affect applications that require this functionality. An example of an application like this is
Microsoft Clustering, which requires systems to effectively share a MAC address. This will
also affect how a layer 2 bridge will operate. This will also affect applications that require a
specific MAC address for licensing. An exception should be made for the port groups that
these applications are connected to. Reject MAC Changes can be set at the vSwitch and/or
the Portgroup level. You can override switch level settings at the Portgroup level.
Solution
1. In the vSphere Web Client, navigate to the host.
2. 'Hosts and Clusters' -> 'vCenter' -> host.
3. On the Manage tab, click Networking, and select Virtual switches.
4. Select a standard switch from the list and click the pencil icon to edit settings.
5. Select Security.
6. Set MAC Address Changes to 'Reject'.
7. Click 'OK'.Additionally, perform the following to implement the recommended configuration state
using the ESXi shell-# esxcli network vswitch standard policy security set -v vSwitch2 -m false
Impact-This will prevent VMs from changing their effective MAC address. It will affect applications
that require this functionality. An example of an application like this is Microsoft Clustering,
which requires systems to effectively share a MAC address. This will also affect how a layer
2 bridge will operate. This will also affect applications that require a specific MAC address
for licensing. An exception should be made for the port groups that these applications are
connected to.