200-901 Network Fundamentals Practice Question
In an SDN architecture, which API is used by the controller to communicate with network devices to install forwarding rules?
⚠ Common exam trap
Cisco often tests the distinction between northbound and southbound APIs; the trap here is confusing the REST API (commonly northbound) with the southbound API that directly programs device forwarding tables.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Southbound API
In SDN, the southbound API is the interface between the controller and the network devices (switches, routers). It allows the controller to install forwarding rules, such as flow entries in OpenFlow switches, enabling centralized control of the data plane.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Southbound API
Why this is correct
Correct. Southbound APIs push rules to devices.
- ✗
REST API
Why it's wrong here
REST is a style, not a specific SDN API direction.
- ✗
East-West API
Why it's wrong here
Not a standard SDN API term.
- ✗
Northbound API
Why it's wrong here
Northbound API is for applications to communicate with the controller.
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