For TAP config add note about promiscuious packets in VMware

[Andy Martin]

I've spent the better part of a day troubleshooting the TAP Server config for OpenVPN as described here:

https://help.ubuntu.com/12.04/serverguide/openvpn.html

 I finally found that the reason it wasn't working was that if your Ubuntu server is running as a VMware VM, you must change the vSwitch properties on the ESXi server to Allow promiscuous mode.

Symptoms: Able to ping server, but nothing on the lan
Resolution: Adjust vSwitch properties as shown here: http://www.datadisk.co.uk/html_docs/vmware/networking.htm

Credit for the hint: http://www.serverubuntu.it/openvpn-bridge-configuration

I just want to save others the trouble. The guide should mention this with the prevalence of VMs today.