Finally I have found it! Citrix's XenServer switch configuration best practices document. While everyone in the world has blog posts and documentation regarding how to set up and configure bridged networks in Xen, they hardly ever go into the physical switch configuration required. This is the document that you will need to pass along to your friendly Network Administrator, as they will more than likely not be familar with networking for Xen as its much different from networking for Vmware ESX.