Cisco CCNA (200-301)Automation and ProgrammabilityMedium
A network designer is implementing Cisco SD-Access and explains the architecture to a colleague. She describes a component that carries encapsulated user traffic between edge nodes using VXLAN, logically separate from the physical topology used for basic IP reachability. Which term describes this VXLAN-based traffic-carrying layer?
- AOverlay network
- BUnderlay network
- CManagement plane
- DControl plane node
Show answer & explanationAnswer & explanation
Correct answer: A. Overlay network
In SD-Access, the overlay network is the logical topology built on top of the physical underlay, using VXLAN encapsulation to carry user traffic between fabric edge nodes independent of the underlying physical addressing scheme.
Why the other options are wrong
- B. The underlay is the physical IP network providing basic reachability between fabric nodes, not the encapsulated traffic layer.
- C. The management plane handles monitoring and configuration, unrelated to VXLAN tunneling.
- D. Control plane nodes handle endpoint registration/lookup (LISP), not traffic encapsulation itself.
SD-Access Overlay
The logical VXLAN-based network built on top of the physical underlay in Cisco SD-Access, used to carry encapsulated user traffic between fabric edge nodes.
- Uses VXLAN encapsulation for data plane traffic
- Runs independently of physical topology (underlay)
- Enables mobility and segmentation across the fabric
Memory trick: Underlay is the road, overlay is the tunnel traffic rides through.