SDN Framework Models: Augmented vs Hybrid
A software-defined network can be defined as a network with an API that allows applications to understand and react to the state of the network in near real time. A vendor is building an SDN solution that exposes an API to the RIB and potentially the forwarding engine directly. The solution provides off-box processes with the capability to interact with the routing table in the same way as a distributed routing process. Which SDN framework model does the solution use?
Community Votes
78% of anonymous learners picked answer C. Votes are pick records left by other test-takers — they are not the verified answer.
Community Insight
The key is recognizing that 'distributed' implies a centralized controller pushing updates, whereas 'augmented' involves an external application or process accessing the local RIB/FIB directly without a central SDN controller managing the entire state.
This question distinguishes between SDN framework models based on the degree of control plane integration. The correct model allows off-box processes to interact directly with the routing table and forwarding engine.
Candidates often choose 'Hybrid' because it sounds like a mix of traditional and SDN, but the specific capability of off-box interaction with the RIB points strictly to the Augmented model definition in Cisco's SDN architecture.
Community Discussion (3 comments)
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Expert Analysis
Why the Answer Is Correct
The Augmented SDN model is characterized by an external controller or application that interacts with the network devices' existing control plane (RIB) and data plane (FIB). This allows for enhanced capabilities without replacing the distributed routing protocols. The scenario describes exactly this: off-box processes interacting with the routing table as if they were a distributed process, which is the hallmark of the Augmented model.Why the Other Options Are Wrong
Replace refers to a fully centralized SDN where the controller replaces the device's control plane entirely. Distributed is not a standard SDN framework classification in this context; rather, traditional networks are distributed. Hybrid typically implies a combination of centralized and distributed control planes coexisting in a more complex manner, but the specific mechanism of 'off-box interaction with RIB' aligns best with Augmented.Community Comment Notes
Community consensus heavily favors option C (Hybrid), likely due to confusion about the term 'hybrid' meaning a mix of old and new. However, as noted by users discussing the definitions, the Augmented model specifically enables applications to react to network state via APIs to the RIB. One user correctly identified that Augmented allows a controller to apply policy, distinguishing it from Replace.Official Reference
Exam Strategy
Focus on the precise definitions of SDN frameworks: Replace (Centralized), Augmented (External/Off-box access to local state), and Overlay (Encapsulation). Memorize the specific interactions allowed in each model to avoid confusion between Augmented and Hybrid.
Frequently Asked Questions
What is the difference between Augmented and Hybrid SDN?
Augmented adds external capabilities to existing distributed control planes, while Hybrid combines centralized SDN controllers with traditional distributed protocols.