Older versions of VMware ESX and VMware Server may require that the virtual NICs be manually set to promiscuous mode.  Depending on the VMware product, accomplishing this may require adding an entry to a VMware configuration file or finding the right configuration option in the configuration menus.

If the VMware NIC cannot be set to promiscuous mode, treat the VMware NIC like a wireless NIC.  Create a bridged TAP adapter or assign the NICs MAC address to the virtual Alpha NIC.  All the caveats in Networking with Wireless Ethernet apply.