Which Cisco SD-WAN overlay protocol exchanges routing, policy, and topology information between controllers and WAN Edge devices?

• A. STP
• B. LACP
• C. OMP
• D. VTP

Answer: (C)

In Cisco SD-WAN, the control-plane that moves routing, policy, and topology data between the orchestration layer and the edge devices is handled by Overlay Management Protocol. This protocol is what vSmart and other controllers use to share VPN routes, policy definitions (security, QoS, service chaining), and the map of how sites are connected across the WAN. With OMP, each WAN Edge learns which paths to use for each VPN, what policies to apply to traffic, and how the overall overlay topology should be constructed, enabling dynamic, centralized, policy-driven routing and path selection.

The other protocols listed are not part of the SD-WAN overlay control plane. Spanning Tree Protocol is used to prevent loops at Layer 2 in traditional Ethernet networks. Link Aggregation Control Protocol is for combining multiple physical links into a single logical link. VLAN Trunking Protocol manages VLANs across switches. They don’t handle the routing, policy distribution, and topology information exchanged between SD-WAN controllers and edge devices.