- A
Southbound API
Correct. Southbound APIs push rules to devices.
- B
REST API
Why wrong: REST is a style, not a specific SDN API direction.
- C
East-West API
Why wrong: Not a standard SDN API term.
- D
Northbound API
Why wrong: Northbound API is for applications to communicate with the controller.
Question 14 of 1,000
200-901 Network Fundamentals Practice Question
This 200-901 practice question tests your understanding of network fundamentals. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
In an SDN architecture, which API is used by the controller to communicate with network devices to install forwarding rules?
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
REST API
- ✗
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
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.
Detailed technical explanation
How to think about this question
Southbound APIs commonly use protocols like OpenFlow (e.g., OpenFlow 1.3) or NETCONF/YANG models. In OpenFlow, the controller sends FlowMod messages to install flow entries in the switch's flow table, specifying match fields, actions, and priority. A real-world scenario is a Cisco ACI fabric where the APIC controller uses OpFlex (a southbound protocol) to push policy-based forwarding rules to leaf switches.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 200-901 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this 200-901 question test?
Network Fundamentals — This question tests Network Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this 200-901 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
This 200-901 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-901 exam.
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