Which innovation in the Cisco NX-OS Software brings an entirely new Layer 2 data plane by encapsulating the frames entering the device with a header that consists of a routable source and destination

OTV (Overlay Transport Virtualization) is a Cisco NX-OS feature that provides Layer 2 extension across disparate IP networks, often used for data center interconnect. It encapsulates original Layer 2 Ethernet frames into a new IP packet with a routable source and destination IP address, enabling the Layer 2 domain to span across Layer 3 boundaries while maintaining MAC address learning separation.

MPLS (Multiprotocol Label Switching) uses labels for forwarding packets but does not encapsulate Layer 2 frames with a routable IP header in the manner OTV does for data center interconnect.

Routing is the general process of forwarding packets between networks based on IP addresses and is not an innovation for a new Layer 2 data plane with encapsulation.

RSTP (Rapid Spanning Tree Protocol) is a Layer 2 protocol for loop prevention within an Ethernet network and does not involve encapsulating frames with routable headers.

LISP (Locator/ID Separation Protocol) separates endpoint identifiers from routing locators, but it's not primarily a Layer 2 data plane encapsulation technology for stretching Layer 2 across data centers.