After you upgrade v Center Server or the ESXi host to v Sphere 5.1 Update 3 and attempt to connect to the v Center Server or the ESXi host using a version of v Sphere Client earlier than 5.1 Update 1b, you are prompted to upgrade the v Sphere Client to v Sphere Client 5.1 Update 3. You must use only the upgraded v Sphere Client to access v Sphere 5.1 Update 3.
The VMware Product Interoperability Matrix provides details about the compatibility of current and earlier versions of VMware v Sphere components, including ESXi, v Center Server, the v Sphere Web Client, and optional VMware products.
Beginning with v Sphere 5.1, support level changes for older guest operating systems have been introduced.
For descriptions of each support level, see Knowledge Base article 2015161.
As in previous v Sphere releases, Cisco Application Virtual Switch (AVS) is not supported.
To determine which processors are compatible with this release, see the VMware Compatibility Guide.The VMware Compatibility Guide provides detailed support information for all operating system releases and VMware product releases.VMware supports Cisco Nexus 1000V with v Sphere 5.1.For more information about Cisco Nexus 1000V, see the Cisco Release Notes.
In addition, go to this site for information about supported management and backup agents before installing ESXi or v Center Server.The v Sphere Client and the v Sphere Web Client are packaged with the v Center Server and modules ZIP file.