After you change the MAC address in the guest operating system of an SR-IOV enabled virtual machine, the virtual machine loses connectivity.

Problem

When you connect the network adapter of a virtual machine to an SR-IOV virtual function (VF), you create a passthrough network adapter for the virtual machine. After the (VF) driver in the guest operating system modifies the MAC address for the passthrough network adapter, the guest operating system shows that the change is successful but the VM network adapter loses connectivity. Although the guest operating system shows that the new MAC address is enabled, a log message in the /var/log/vmkernel.log file indicates that the operation has failed. 

Requested mac address change to new MAC address on port VM NIC port number, disallowed by vswitch policy.

where

  • new MAC address is the MAC address in the guest operation system.
  • VM NIC port number is the port number of the VM network adapter in hexadecimal format.

Cause

The default security policy on the port group to which the passthrough network adapter is connected does not allow changes in the MAC address in the guest operating system. As a result, the networking interface in the guest operating system cannot acquire an IP address and loses connectivity.

Solution

  • ♦ In the guest operating system, reset the interface to cause the passthrough network adapter to regain its valid MAC address. If the interface is configured to use DHCP for address assignment, the interface acquires an IP address automatically.
    For example, on a Linux virtual machine run the ifconfig console command. 
    ifconfig ethX down
ifconfig ethX up

    where X in ethX represents the sequence number of the virtual machine network adapter in the guest operating system.