VMWare Switch Is a Hub
While preparing materials for my new class TCP/IP Weapons School I needed to test how the virtual switch in VMware Server behaves. I started three VMs. All had lnc0 interfaces bridged to the host's physical NIC. Two VMs had IPs 192.168.2.51 and 192.168.2.52 assigned. The third VM had no IP assigned. When 192.168.2.51 pinged 192.168.2.52, the third VM was able to see the ICMP traffic. This means the virtual switch in VMware Server appears to behave like a hub. This makes monitoring traffic easier.
Comments
This post on the VMTN forums is the best description and howto I've seen on promiscuous mode and ESX.
http://www.vmware.com/community/message.jspa?messageID=371562