Ccna certification Practice Tests

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Appendix 

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  Answers to Practice Test Questions

 17.  B.  Controller-based networking has a logically centralized control plane to centrally 

control the data plane. The data plane is not centralized because switching and routing 

of data must be done very fast, usually with the use of application-specific integrated 

circuits (ASICs). Controller-based networking comes in many different forms, ranging 

from applications to hardware appliances. Both controller-based network switching and 

autonomous network switching use ASICs, but controller-based network switches do not 

centrally switch frames.

 18.  Software-Defined Wide Area Network (SD-WAN) is the term commonly used to describe 

the combination of multiple sites to act as one single network. Use cases of SD-WAN 

are disaster recovery and remote office and branch office planning. software-defined 

networking (SDN) is the term used to describe local area network (LAN) controller-based 

networking. SD-LAN is not a term commonly used, and therefore, option C is an invalid 

answer. A virtual private network (VPN) will allow multiple sites to act as one single 

network, but it is not centrally controlled with controller-based networking.

 19.  C.  Controller-based networking, also known as software-defined networking (SDN), 

is roughly 15 years old. Many see this maturity as a disadvantage when comparing it to 

traditional networking equipment that is much older in theory. Scalability, security, and 

centralized provisioning are advantages to using controller-based networking and far 

outweigh the disadvantage of the youth of SDN.

 20.  C.  Quality of service (QoS) can be directly controlled with an SDN controller. The 

SDN controller will push programming to the SDN-enabled switch so that the switch 

can control the flow of traffic. CPU and memory utilization can be reported upon, and 

arguably programming can be pushed out to alleviate central processing unit (CPU) and 

memory utilization, but CPU and memory utilization is not directly controlled with an 

SDN controller. The forwarding of traffic is a responsibility of the data plane, which can 

be changed by the control plane. However, the SDN controller does not forward packets 

explicitly; that is the function of the switch.

 21.  B.  All software-defined network (SDN) switches are stateless with respect to their 

configuration. The configuration is applied from the central controller, and therefore, any 

configuration contained on the switch does not matter if it is lost during a reboot. Data is 

not centrally switched at the SDN controller; this would make data transfer too slow and 

overburden the SDN controller. The data flowing through the switch is not consequential 

to the SDN controller; some data flows can be stateless, such as UDP, and some can be 

stateful, such as TCP.

 22.  A.  The Simple Network Management Protocol (SNMP) allows for the central monitoring 

of switches and routers by using traps and polling of network metrics. Syslog is a method 

of collecting logs for passive analysis after an event has been brought to your attention. 

Software-defined networking (SDN) allows for the centralized control of switches and 

routers. The Cisco Discovery Protocol (CDP) is used to discover Cisco devices on the 

immediate network.

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Chapter 6: Automation and Programmability (Domain 6)