1|Page
WGU D415 – SOFTWARE-DEFINED NETWORKING
(SDN) COMPREHENSIVE OBJECTIVE ASSESSMENT
ACTUAL EXAM PREP 2026 ALL QUESTIONS AND
CORRECT DETAILED ANSWERS WITH RATIONALES
ALREADY A GRADED WITH EXPERT FEEDBACK
|NEW ND REVISED
Question 1
What is the primary architectural change introduced by Software-
Defined Networking (SDN)?
A. Combining the control and data planes into a single device
B. Decoupling the network control (control plane) from the
forwarding functions (data plane)
C. Eliminating all network protocols
D. Replacing IP addresses with MAC addresses
Rationale: SDN fundamentally separates the control plane (decision-
making) from the data plane (packet forwarding). This decoupling
allows the control plane to be centrally managed and programmed
directly, while the data plane remains responsible for high-speed
packet forwarding based on instructions from the controller. This
centralization enables network programmability, automation, and
dynamic resource allocation.
Question 2
In SDN, which plane is responsible for making forwarding decisions?
A. Management plane
B. Control plane
C. Data plane
D. Orchestration plane
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Rationale: The control plane is responsible for making routing and
switching decisions. It contains the logic that determines how traffic
should be forwarded. In SDN, this logic is centralized in the SDN
controller, which then programs the data plane devices (switches) with
forwarding instructions. The data plane forwards packets based on
those instructions.
Question 3
What does the data plane in an SDN architecture primarily do?
A. Runs routing protocols like OSPF
B. Provides a RESTful API to applications
C. Forwards packets according to flow table entries
D. Authenticates users to the network
Rationale: The data plane handles the actual forwarding of packets,
using flow tables populated by the SDN controller. It does not make
independent forwarding decisions but rather executes the instructions
it receives from the control plane. This separation allows the data
plane to be simplified and optimized for high-speed packet processing.
Question 4
Which type of API is used for communication between an SDN
controller and applications?
A. Southbound API
B. East–west API
C. Northbound API
D. Management API
Rationale: The northbound API is used for communication between
the SDN controller and applications. It allows applications to request
network services and abstract the underlying network complexity.
Southbound APIs are used for communication between the controller
and the data plane devices (switches). East-west APIs are used for
communication between multiple controllers.
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Question 5
Which southbound protocol is most commonly associated with SDN and
defines a standard for communication between the controller and
switches?
A. NETCONF
B. OpenFlow
C. RESTCONF
D. OVSDB
Rationale: OpenFlow is the most widely known southbound protocol
in SDN. It defines a standard for communication between the SDN
controller and the data plane switches, allowing the controller to
program flow tables on the switches. While NETCONF, RESTCONF,
and OVSDB are also used in SDN environments, OpenFlow is the
protocol most specifically associated with the separation of control and
data planes.
Question 6
Which of the following is a key function of an SDN controller?
A. Packet forwarding at wire speed
B. Maintaining a global view of the network
C. Encapsulating packets for overlay networks
D. Providing physical connectivity between switches
Rationale: A primary function of the SDN controller is to maintain a
global, centralized view of the network topology and state. This global
view enables the controller to make intelligent forwarding decisions
and optimize network performance. The controller does not perform
packet forwarding (that is the data plane's role) but rather programs
the forwarding devices.
Question 7
OpenStack Swift is used for:
, 4|Page
A. Compute resource management
B. Object storage for unstructured data
C. Networking as a service
D. Identity and authentication
Rationale: OpenStack Swift is an object storage system designed for
scalability and durability. It is ideal for storing large amounts of
unstructured data such as backups, images, and media files. Swift
distributes data across multiple nodes, improving fault tolerance and
performance. Unlike block storage, it does not rely on a single point of
failure. Nova handles compute, Neutron handles networking, and
Keystone handles identity.
Question 8
Which OpenStack module provides authentication for accessing all
OpenStack services?
A. Nova
B. Glance
C. Keystone
D. Neutron
Rationale: Keystone is the OpenStack module that provides identity,
authentication, and authorization services for all OpenStack
components. It manages users, projects, roles, and service catalogs.
Nova is the compute module, Glance manages VM images, and
Neutron provides networking.
Question 9
Which approach improves the strength of software-defined networking
(SDN) security and intrusion tolerance?
A. Controller diversity
B. Controller consolidation
C. Logging
D. Virtualization
WGU D415 – SOFTWARE-DEFINED NETWORKING
(SDN) COMPREHENSIVE OBJECTIVE ASSESSMENT
ACTUAL EXAM PREP 2026 ALL QUESTIONS AND
CORRECT DETAILED ANSWERS WITH RATIONALES
ALREADY A GRADED WITH EXPERT FEEDBACK
|NEW ND REVISED
Question 1
What is the primary architectural change introduced by Software-
Defined Networking (SDN)?
A. Combining the control and data planes into a single device
B. Decoupling the network control (control plane) from the
forwarding functions (data plane)
C. Eliminating all network protocols
D. Replacing IP addresses with MAC addresses
Rationale: SDN fundamentally separates the control plane (decision-
making) from the data plane (packet forwarding). This decoupling
allows the control plane to be centrally managed and programmed
directly, while the data plane remains responsible for high-speed
packet forwarding based on instructions from the controller. This
centralization enables network programmability, automation, and
dynamic resource allocation.
Question 2
In SDN, which plane is responsible for making forwarding decisions?
A. Management plane
B. Control plane
C. Data plane
D. Orchestration plane
,2|Page
Rationale: The control plane is responsible for making routing and
switching decisions. It contains the logic that determines how traffic
should be forwarded. In SDN, this logic is centralized in the SDN
controller, which then programs the data plane devices (switches) with
forwarding instructions. The data plane forwards packets based on
those instructions.
Question 3
What does the data plane in an SDN architecture primarily do?
A. Runs routing protocols like OSPF
B. Provides a RESTful API to applications
C. Forwards packets according to flow table entries
D. Authenticates users to the network
Rationale: The data plane handles the actual forwarding of packets,
using flow tables populated by the SDN controller. It does not make
independent forwarding decisions but rather executes the instructions
it receives from the control plane. This separation allows the data
plane to be simplified and optimized for high-speed packet processing.
Question 4
Which type of API is used for communication between an SDN
controller and applications?
A. Southbound API
B. East–west API
C. Northbound API
D. Management API
Rationale: The northbound API is used for communication between
the SDN controller and applications. It allows applications to request
network services and abstract the underlying network complexity.
Southbound APIs are used for communication between the controller
and the data plane devices (switches). East-west APIs are used for
communication between multiple controllers.
,3|Page
Question 5
Which southbound protocol is most commonly associated with SDN and
defines a standard for communication between the controller and
switches?
A. NETCONF
B. OpenFlow
C. RESTCONF
D. OVSDB
Rationale: OpenFlow is the most widely known southbound protocol
in SDN. It defines a standard for communication between the SDN
controller and the data plane switches, allowing the controller to
program flow tables on the switches. While NETCONF, RESTCONF,
and OVSDB are also used in SDN environments, OpenFlow is the
protocol most specifically associated with the separation of control and
data planes.
Question 6
Which of the following is a key function of an SDN controller?
A. Packet forwarding at wire speed
B. Maintaining a global view of the network
C. Encapsulating packets for overlay networks
D. Providing physical connectivity between switches
Rationale: A primary function of the SDN controller is to maintain a
global, centralized view of the network topology and state. This global
view enables the controller to make intelligent forwarding decisions
and optimize network performance. The controller does not perform
packet forwarding (that is the data plane's role) but rather programs
the forwarding devices.
Question 7
OpenStack Swift is used for:
, 4|Page
A. Compute resource management
B. Object storage for unstructured data
C. Networking as a service
D. Identity and authentication
Rationale: OpenStack Swift is an object storage system designed for
scalability and durability. It is ideal for storing large amounts of
unstructured data such as backups, images, and media files. Swift
distributes data across multiple nodes, improving fault tolerance and
performance. Unlike block storage, it does not rely on a single point of
failure. Nova handles compute, Neutron handles networking, and
Keystone handles identity.
Question 8
Which OpenStack module provides authentication for accessing all
OpenStack services?
A. Nova
B. Glance
C. Keystone
D. Neutron
Rationale: Keystone is the OpenStack module that provides identity,
authentication, and authorization services for all OpenStack
components. It manages users, projects, roles, and service catalogs.
Nova is the compute module, Glance manages VM images, and
Neutron provides networking.
Question 9
Which approach improves the strength of software-defined networking
(SDN) security and intrusion tolerance?
A. Controller diversity
B. Controller consolidation
C. Logging
D. Virtualization
