What is a characteristic of the overlay network in the Cisco SD-Access architecture?

The correct answer is D. It provides isolation among the virtual networks and independence from the physical network.

Cisco SD-Access is based on two main layers:

Underlay network → Physical infrastructure (routers, switches, IP connectivity)

Overlay network → Virtualized logical network built on top of the underlay

According to Cisco ENCOR architecture principles, the overlay network:

Uses technologies like LISP (control plane) and VXLAN (data plane)

Creates virtual networks (VNs) for segmentation

Provides end-to-end logical separation (macro-segmentation)

Is independent of the physical topology

Enables scalable and flexible network design

Thus, the overlay abstracts the complexity of the underlay and ensures isolation between different user groups, departments, or tenants.

Directly describes virtual network segmentation

Matches Cisco’s definition of overlay abstraction and independence

Core principle of SD-Access fabric design

A. Multicast and Layer 2 flooding relate more to underlay or legacy designs, not overlay behavior.

B. Describes the underlay network (physical devices), not overlay.

C. Refers to traditional network design, which SD-Access replaces.

Underlay = Physical IP network (reachability)

Overlay = Virtual segmentation & policy (VXLAN + LISP)

Overlay = Abstraction + Segmentation + Independence