CompTIA Network+ (N10-009)Networking ConceptsHard
A network engineer is designing an SDN deployment and needs the controller to install forwarding rules directly onto physical switches using a standardized communication protocol. Which type of interface accomplishes this?
- ANorthbound API
- BEast-west interface
- CManagement plane interface
- DSouthbound API
Show answer & explanationAnswer & explanation
Correct answer: D. Southbound API
The southbound API (such as OpenFlow) connects the SDN controller to the underlying network devices, allowing it to push forwarding rules and configuration down to switches and routers in the data plane.
Why the other options are wrong
- A. The northbound API connects the controller to applications and orchestration systems above it, not to switches.
- B. East-west traffic/interfaces refer to communication between controllers or servers within a data center, not controller-to-switch programming.
- C. Management plane interfaces handle device administration but are not the defining SDN controller-to-device link.
SDN Southbound API
The interface used by an SDN controller to communicate with and program the underlying network devices (switches/routers) in the data plane, commonly using protocols like OpenFlow.
- Connects controller to physical/virtual switches
- OpenFlow is a common southbound protocol
- Contrasts with northbound API, which connects controller to applications
Memory trick: Southbound goes down to devices; northbound goes up to apps.