hardMultiple ChoiceObjective-mapped
CISSP Practice Question: In a software-defined network (SDN) architecture,…
In a software-defined network (SDN) architecture, the control plane is separated from the data plane. A network administrator is troubleshooting packet forwarding delays. Which plane is directly responsible for forwarding packets?
⚠ Common exam trap
ISC2 often tests the misconception that the control plane is responsible for forwarding because it makes routing decisions, but in SDN the control plane only programs the data plane, which actually performs the forwarding.
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
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Data plane
In SDN, the data plane (also called the forwarding plane) is directly responsible for forwarding packets based on flow table entries installed by the controller. It handles per-packet operations like looking up destination addresses, applying actions (e.g., output to port, drop, modify header), and forwarding at line rate. Packet forwarding delays are typically caused by data plane issues such as flow table misses, hardware forwarding pipeline congestion, or inefficient TCAM lookups.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Data plane
Why this is correct
In an SDN architecture, the data plane, also known as the forwarding plane, is directly responsible for the physical movement of network traffic. It comprises the network devices (e.g., switches, routers) that execute the forwarding rules, or "flow tables," pushed down by the control plane. Its primary function is high-speed packet forwarding, encapsulation, and decapsulation, strictly adhering to the instructions received to direct packets to their next hop.
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Application plane
Why it's wrong here
The application plane in SDN resides at the highest level, comprising various network applications and services that communicate with the control plane to request or provide network resources and policies. These applications, such as load balancers, firewalls, or network analytics tools, focus on delivering high-level network services and policy orchestration. It does not directly participate in the forwarding of individual packets, but rather defines the desired network behavior.
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Control plane
Why it's wrong here
The control plane is the "brain" of the SDN architecture, responsible for making all forwarding decisions and maintaining a global, centralized view of the network topology and state. It communicates with the data plane devices to program their flow tables, dictating how traffic should be handled and routed. While it determines the path and rules for packet flow, it does not physically process or forward the packets itself; that task is delegated to the data plane.
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Management plane
Why it's wrong here
The management plane is concerned with the operational aspects of the network, including monitoring network device health, configuring device parameters, and performing administrative tasks such as software updates, troubleshooting, and user authentication. It provides the interface for administrators to interact with the SDN infrastructure, ensuring proper functioning and resource allocation. This plane is distinct from data forwarding, which is a real-time traffic handling function.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CISSP practice question is part of Courseiva's free ISC2 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 CISSP exam.