When does this design benefit a virtualized data center?

A.
The access layer and core switches use several layers of redundancy protocols, including
Multiple Spanning Tree Protocol (MSTP) at Layer 2, Virtual Router Redundancy Procotol (VRRP)
at Layer 3, and Intelligent Resilient Framework (IRF) at Layer 4.

B.
The access layer and core switches can connect on link aggregation groups. VLANs can
extend across these aggregations, but they are more stable and highly-available than redundant
Layer 2 links that use spanning tree.

C.
The access layer switches can integrate their Intelligent Resilient Framework (IRF) capabilities
with those on the core switches to create a single CLOS fabric.

D.
The core switches can implement Virtual Ethernet Port Aggregator (VEPA) to extend tunnels for
virtualized traffic across the data center backbone.

Explanation: