For cisco Nexus fans -
Cisco Overlay Transport Virtualization (OTV) explained in plain and simple language.
To have better application availablity and flexible allocation of the workload, we need seamless connectivity among our datacenters dispersed geographically. Cisco's OTV provide Layer 2 and 3 and storage connectivity between
data centers. Connectivity must be provided without compromising the
autonomy of data centers or the stability of the overall network.
The video below is intended to understand OTV better