N10-009 Network Implementation Practice Question

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

  The Southbound API serves as the critical interface through which the SDN controller directly communicates with and programs the underlying network infrastructure devices, such as switches and routers. Protocols like OpenFlow, NETCONF, and OVSDB are common examples, enabling the controller to dynamically install flow rules, modify forwarding tables, and retrieve operational state from the data plane elements. This direct interaction allows for centralized control and configuration of the network's forwarding behavior, making it the correct choice for a network architect implementing device configuration.

• ✗

  Northbound API

  Why it's wrong here

  The Northbound API provides an abstract interface for applications, orchestration platforms, and business logic to interact with the SDN controller. This API abstracts the underlying network complexity, allowing higher-level applications to request network services, define policies, and monitor network performance without needing to understand the specifics of individual network devices. It enables automation and programmability by translating application requirements into network configurations, but it is not used for direct controller-to-device communication.

  When this WOULD be correct

  A question asks: 'Which API allows an SDN application to request network services from the SDN controller?' In that context, the Northbound API is correct because it enables applications to interact with the controller.

• ✗

  Eastbound API

  Why it's wrong here

  An Eastbound API facilitates communication and coordination between multiple SDN controllers within a distributed control plane architecture. This interface is crucial for ensuring consistency and synchronization of network state across different controller instances, especially in large-scale deployments or when implementing high availability and load balancing for the control plane. It enables controllers to share information and collectively manage the network, preventing conflicts and ensuring a unified view, but does not directly configure network devices.

  When this WOULD be correct

  In a multi-domain SDN environment, an Eastbound API is used for inter-controller communication to exchange network state information and coordinate policies between controllers in different administrative domains.

• ✗

  Westbound API

  Why it's wrong here

  The Westbound API, often considered conceptually similar to the Eastbound API, also defines the communication channels between SDN controllers. While the specific directional nomenclature can vary based on vendor or architectural perspective, its primary function remains to enable inter-controller communication for tasks like state synchronization, policy enforcement across controller domains, and distributed decision-making. It supports horizontal scaling and resilience by allowing controllers to operate cooperatively, rather than directly configuring individual network devices.

  When this WOULD be correct

  In a scenario where an SDN controller needs to interact with a non-SDN network or a legacy device using a proprietary protocol, a Westbound API might be used to bridge the SDN domain with external systems.

Option-by-option analysis

Why each answer is right or wrong

Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.

Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”

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