Which protocol is best suited for connecting two data centers together?

LISP focuses on decoupling endpoint identity from location for optimal routing and mobility, but it is not a direct Layer 2 extension protocol like OTV for connecting data centers.

OTV (Overlay Transport Virtualization) is a Cisco-developed protocol specifically designed for data center interconnect (DCI) that extends Layer 2 segments across an IP transport network, enabling seamless VM mobility and maintaining Layer 2 adjacency between geographically separated data centers.

FabricPath is a Layer 2 multipathing technology used *within* a single data center to provide active-active forwarding and scale, not for interconnecting distinct data centers over a WAN.

vPC (Virtual Port Channel) provides link aggregation and resiliency *within* a data center or to directly connected devices, but it does not extend Layer 2 segments across a WAN to connect distant data centers.