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Fundamentals Practice Exam
Question 1. Which of the following best describes the primary limitation of traditional networking that motivated the development of SDN? A) High bandwidth availability B) Vendor‑specific hardware lock‑in C) Unlimited scalability D) Simple configuration interfaces Answer: B Explanation: Traditional networks often required proprietary hardware and software, making it difficult to integrate equipment from different vendors and leading to lock‑in. Question 2. In the three‑plane model of networking, which plane is responsible for forwarding packets based on flow rules? A) Data Plane B) Control Plane C) Management Plane D) Application Plane Answer: A Explanation: The Data Plane (also called the forwarding plane) handles actual packet forwarding using flow entries. Question 3. What is the main advantage of separating the control plane from the data plane in SDN? A) Increased hardware cost B) Centralized network intelligence and programmability C) Reduced network latency D) Elimination of routing protocols
Fundamentals Practice Exam
Answer: B Explanation: Decoupling allows a central controller to manage the network, providing programmability and global view. Question 4. Which SDN architectural component interacts directly with network applications? A) Data Plane B) Control Plane C) Application Plane D) Management Plane Answer: C Explanation: The Application Plane consists of network‑level applications that request services from the controller. Question 5. Which of the following is a popular open‑source SDN controller that runs on the Apache Karaf OSGi container? A) Open vSwitch B) ONOS C) OpenDaylight D) Cisco DNA Center Answer: C Explanation: OpenDaylight (ODL) uses Apache Karaf and OSGi for modular controller development. Question 6. The northbound interface of an SDN controller primarily provides which type of functionality? A) Direct hardware packet forwarding
Fundamentals Practice Exam
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Answer: B Explanation: OpenFlow 1.1 added the concept of multiple flow tables to enable more complex pipelines. Question 10. Which tool allows rapid creation of virtual SDN topologies for testing and education? A) Wireshark B) Mininet C) GNS D) Cisco Packet Tracer Answer: B Explanation: Mininet emulates hosts, switches, and links in a single Linux kernel, ideal for SDN prototyping. Question 11. When using Mininet, which command creates a linear topology of three switches and two hosts per switch? A) sudo mn --topo linear,3 B) sudo mn --topo tree,3 C) sudo mn --custom linear.py D) sudo mn --topo single,3 Answer: A
Fundamentals Practice Exam
Explanation: The linear,3 argument builds a line of three switches; hosts are attached automatically. Question 12. Which of the following best describes the role of YANG in network programmability? A) A packet‑capture format B) A routing protocol C) A data‑modeling language for configuration and state data D) A physical cable standard Answer: C Explanation: YANG defines hierarchical data models used by NETCONF and RESTCONF for configuration. Question 13. Which of these is a primary benefit of network virtualization in data centers? A) Fixed IP addressing B) Multi‑tenant isolation and flexible provisioning C) Increased physical cabling D) Manual configuration of each VM Answer: B Explanation: Virtual networks enable isolated tenant traffic and rapid provisioning without hardware changes. Question 14. In the context of SDN, what does “overlay network” refer to? A) The physical wiring of the data center B) Logical network built on top of an existing underlay infrastructure C) A backup power system
Fundamentals Practice Exam
A) ovs-vsctl add-flow br0 "tcp,actions=output:2" B) ovs-ofctl add-flow br0 "tcp actions=output:2" C) ovs-ofctl add-flow br0 "tcp,actions=output:2" D) ovs-vsctl set bridge br0 flow tcp output:2 Answer: C Explanation: ovs-ofctl add-flow is used to program OpenFlow flows; the correct syntax includes a comma before actions. Question 18. Which of the following is a key difference between a traditional switch and a software‑defined switch? A) Traditional switches store MAC tables, SDN switches do not store any tables. B) Traditional switches embed control logic in hardware; SDN switches delegate control to an external controller. C) SDN switches cannot support VLANs. D) Traditional switches require a controller for basic forwarding. Answer: B Explanation: Traditional switches run their own control plane; SDN switches forward based on rules supplied by a remote controller. Question 19. In SDN, which layer is primarily responsible for network automation and orchestration? A) Data Plane B) Control Plane C) Management Plane D) Physical Layer Answer: C
Fundamentals Practice Exam
Explanation: The Management Plane handles configuration, monitoring, and automation tasks. Question 20. Which of the following protocols is commonly used for device configuration in modern SDN environments alongside NETCONF? A) FTP B) RESTCONF C) SMTP D) Telnet Answer: B Explanation: RESTCONF provides a RESTful API for accessing YANG‑modeled data, complementing NETCONF. Question 21. Which OpenFlow message type is used by the controller to delete a flow entry from a switch? A) OFPT_PACKET_IN B) OFPT_FLOW_MOD (with command DELETE) C) OFPT_FEATURES_REQUEST D) OFPT_STATS_REPLY Answer: B Explanation: OFPT_FLOW_MOD messages with the DELETE command instruct a switch to remove matching flows. Question 22. What does the term “vendor lock‑in” refer to in networking? A) Ability to use any hardware interchangeably B) Dependence on a single vendor’s proprietary protocols and APIs C) Open standards that all vendors follow
Fundamentals Practice Exam
B) ipv4_dst C) vlan_vid D) tcp_src Answer: C Explanation: vlan_vid matches the VLAN identifier in the Ethernet frame. Question 26. Which of the following best describes NFV (Network Function Virtualization)? A) Virtualizing compute resources only B) Implementing network functions (e.g., firewall, load balancer) as software on commodity hardware C) Replacing all routers with switches D) Using only physical appliances for network services Answer: B Explanation: NFV decouples network functions from dedicated appliances, running them as virtual machines or containers. Question 27. In the context of SDN, what is a “flow rule” primarily used for? A) Defining IP address allocation B) Specifying how matching packets should be processed (forward, drop, modify) C) Configuring physical port speed D) Setting up DHCP leases Answer: B Explanation: Flow rules consist of match criteria and actions applied to matching traffic. Question 28. Which of the following is NOT a typical function of the SDN Management Plane?
Fundamentals Practice Exam
A) Collecting telemetry data B) Programming forwarding behavior on switches C) Authenticating users to the controller D) Performing per‑packet routing decisions Answer: D Explanation: Per‑packet routing decisions are made by the Control Plane (or Data Plane), not the Management Plane. Question 29. Which OpenFlow version introduced the concept of “metadata” fields for passing information between tables? A) 1. B) 1. C) 1. D) 1. Answer: C Explanation: OpenFlow 1.2 added a 64‑bit metadata field to enable inter‑table communication. Question 30. Which of the following best characterizes a “southbound API” in SDN? A) Interface between applications and the controller B) Interface between the controller and network devices C) User‑interface for administrators D) Protocol for external cloud services Answer: B Explanation: Southbound APIs (e.g., OpenFlow, NETCONF) allow the controller to program the data‑plane devices.
Fundamentals Practice Exam
Explanation: Because the controller centrally manages the network, its compromise can affect all connected devices. Question 34. Which protocol is typically used to retrieve statistics from an OpenFlow switch? A) OFPT_STATS_REQUEST B) OFPT_ECHO_REQUEST C) OFPT_FEATURES_REQUEST D) OFPT_PACKET_OUT Answer: A Explanation: OFPT_STATS_REQUEST messages ask the switch for flow, port, or aggregate statistics. Question 35. In a Mininet topology, which Python class represents a virtual switch? A) Host B) Link C) OVSSwitch D) Controller Answer: C Explanation: OVSSwitch is the default switch class used in Mininet, backed by Open vSwitch. Question 36. Which of the following best explains why SDN enables rapid network innovation? A) It eliminates the need for any hardware. B) Network behavior can be changed by software updates without replacing devices. C) It forces all vendors to use identical ASICs.
Fundamentals Practice Exam
D) It uses only static routing tables. Answer: B Explanation: Centralized, programmable control allows new features to be deployed via software. Question 37. Which of the following is a typical use case for SDN in a WAN environment? A) Static VLAN assignment B) Dynamic path selection based on latency C) Manual IP address configuration D) Physical cable management Answer: B Explanation: SDN can steer traffic over multiple links, selecting paths based on real‑time metrics. Question 38. Which OpenDaylight subsystem provides a RESTful API for applications? A) MD‑SAL B) DLUX (Web UI) C) BGP‑Pegasus D) RESTCONF plugin Answer: D Explanation: The RESTCONF plugin exposes YANG‑modeled data via HTTP/REST. Question 39. Which of the following best describes “flow‑based routing” in SDN? A) Routing decisions are made per‑packet using traditional IP routing tables. B) Switches forward packets based on pre‑installed flow entries rather than per‑packet lookup.
Fundamentals Practice Exam
A) odl start B) ./karaf inside the ODL distribution directory C) systemctl start odl D) odl-controller --run Answer: B Explanation: OpenDaylight is launched by executing the Karaf shell script (./karaf). Question 43. Which of the following best explains why OpenFlow switches maintain multiple flow tables? A) To store MAC addresses for each VLAN B) To enable pipeline processing where packets traverse several stages of matching and actions C) To keep backup copies of the same flow D) To separate IPv4 and IPv6 traffic completely Answer: B Explanation: Multiple tables allow a packet to be processed through a sequence of match/action stages. Question 44. Which of the following is an example of a “network function” that can be virtualized using NFV? A) Ethernet cable B) Router ASIC C) Firewall D. 802.11 Wi‑Fi radio Answer: C Explanation: Firewalls, load balancers, and DPI are typical VNFs (Virtual Network Functions).
Fundamentals Practice Exam
Question 45. In an SDN environment, which layer is primarily responsible for collecting real‑time telemetry such as per‑flow byte counts? A) Data Plane B) Control Plane C) Management Plane D) Physical Layer Answer: C Explanation: The Management Plane aggregates telemetry data for monitoring and analytics. Question 46. Which of the following protocols is used by OVSDB to manage Open vSwitch configuration? A) OpenFlow B) NETCONF C) OVSDB (Open vSwitch Database) protocol over TCP D) BGP Answer: C Explanation: OVSDB uses its own protocol (based on JSON‑RPC) over TCP to configure OVS. Question 47. Which of the following is a key advantage of using a “soft‑switch” like OVS in virtualized environments? A) Fixed hardware forwarding speed B) Ability to run on commodity servers and be programmatically controlled C) Requires proprietary ASICs D) Cannot be integrated with SDN controllers Answer: B Explanation: Soft‑switches run in software, are flexible, and can be managed by SDN controllers.
Fundamentals Practice Exam
Explanation: TLS encrypts and authenticates OpenFlow messages, preventing tampering. Question 51. Which of the following statements about the “control plane” in a traditional router is true? A) It forwards packets at line rate. B) It runs distributed routing protocols like OSPF locally on the device. C) It is always located in a remote data center. D) It does not store routing tables. Answer: B Explanation: In traditional routers, the control plane runs routing protocols locally to compute forwarding tables. Question 52. In a multi‑tenant data center, which SDN feature enables each tenant to have an isolated virtual network? A) Shared VLANs only B) VXLAN with unique VNI per tenant C) Single flat L2 domain D) Physical segregation of cables Answer: B Explanation: VXLAN assigns a unique Virtual Network Identifier (VNI) to separate tenant traffic. Question 53. Which of the following best describes the role of “northbound” APIs in an SDN controller? A) They provide low‑level hardware access to ASICs. B) They expose abstracted services to applications and orchestration tools. C) They handle packet‑in events from switches.
Fundamentals Practice Exam
D) They configure physical port speeds. Answer: B Explanation: Northbound APIs allow external applications to request network services without dealing with low‑level details. Question 54. Which OpenFlow match field would you use to identify traffic from a specific TCP source port? A) tcp_src B) udp_dst C) icmp_type D) eth_type Answer: A Explanation: tcp_src matches the TCP source port number. Question 55. In the context of SDN, what does “flow timeout” refer to? A) The time a switch takes to boot up B) The period after which an idle flow entry is removed from the table C) The delay between controller and switch connection D) The time taken to compile YANG models Answer: B Explanation: Flow entries can have idle or hard timeouts; after expiration they are deleted. Question 56. Which of the following is a typical reason to use a “group table” in OpenFlow? A) To store VLAN IDs B) To implement fast failover or multicast actions
