Interview Questions : CCNA | Network Security

This is questions and answers series of CCNA interview questions. For those who don’t know about CCNA, for that CCNA is network certification, short for Cisco Certified Network Associate Routing & Switching (CCNA) certification. Passing this certification validates the ability 0f candidates to install, configure, operate, and troubleshoot medium-size routed and switched networks.

Q1. What is the purpose of the Data Link?

Ans: Data Link is the second layer out of seven layers of the OSI model. OSI model stands for Open Systems Interconnection model and it is used as a standard to communicate digital data from source to destination.

For incoming data, the Data Link layer detects and corrects errors in the data stream coming from the physical layer.

For outgoing data, this layer receives data from the network layer and converts it into frames. Later, provide addressing information by adding the header to each frame. It also provides a flow control mechanism and an error control mechanism.

Q2. When does network congestion occur?

Ans: Network Congestion is a term when there is so much data in the network layer that it slows down network response time.

Congestion is the main reason for deteriorating quality in terms of data packet loss and more latency.

Q3. Differentiate full-duplex from half-duplex.

Ans: In simple words, there is two-way communication at the same time in full-duplex communication while in half-duplex communication, two-way communication is there but not simultaneously.

Q4. What is Network latency?

Ans: Latency is a term used to denote the time duration for getting output after providing input. Ideally, network latency should be zero.

Q5. Explain the benefits of VLANs.

Ans: A virtual LAN (VLAN) is a combination of one or more LANs configured so that all the work systems are on the same network virtually.


  • If configured correctly, it improves the performance of a network.
  • Improves the overall security of the network.

Q6. How does RIP differ from IGRP?

Ans: RIP and IGRP are different routing protocols. RIP stands for Routing Information Protocol while IGRP stands for Interior Gateway Routing Protocol. RIP and IGRP both are distance vector protocols.

RIP takes the best route decision to the network based on the number of hops in order to determine the best route to a network while IGRP takes the best route decision to the network based on bandwidth, reliability, MTU, and hop count.

Q7. What are the different memories used in a CISCO router?

Ans: Here is the list of memories used in the CISCO router:

  • ROM (Read Only Memory)
  • RAM (Random Access Memory)
  • Flash RAM
  • NVRAM (Non-Volatile Random Access Memory)

Q8. What is 100BaseFX?

Ans: 100BASE-X also referred to as "Fast Ethernet". It provides a data transmission speed of 100 Mbps using a baseband.

Q9. What are the advantages of a layered model in the networking industry?

Ans: Here are the advantages of a layered model in the networking industry:

  • Promote industry standardization by providing the role of the different layers.
  • Network Administrators are able to troubleshoot network problems easily in a layer without affecting the other layers.

Q10. What is HDLC?

Ans: HDLC stands for High-level Data Link Control. It refers to the group of rules and protocols for transmitting data from different network nodes.

Q11. What is Routing?

Ans: Routing is the process of identifying the path for traffic in a network, or between or across multiple networks.

Q12. What is BootP?

Ans: BootP is also called Boot Program. This protocol basically assigns an IP address when the computer is connected to a network and boots its operating system.

Q13. How does cut-through LAN switching work?

Ans: In Cut-Through LAN switching, the router forwards the frame to the next segment as soon as it reads the destination address without waiting for the whole frame.

Q14. What are the different IPX access lists?

Ans: Standard and Extended are the different IPX access lists.

Standard Access List filters network traffic based only on the source or destination IP address.

An Extended Access List filters network traffic based on source and destination IP addresses, ports, sockets, and protocols.

Q15. What’s the simplest way to remotely configure a router?

Ans: Cisco AutoInstall Procedure is available to remotely configure a router. Obviously, you need to connect the internet or LAN to the router.

Q16. How are internetworks created?

Ans: Internetwork is a collection of many different networks to create a large network. Internetworks are created by using routers to connect different networks.

Q17. Give some benefits of LAN switching.

Ans: Here are some benefits of LAN switches:

  • Increased network scalability
  • less congestion
  • low latency
  • No single point of failure
  • Improved bandwidth performance
  • More network connections simultaneously

Q18. Briefly, explain the conversion steps in data encapsulation.

Ans: When a user sends an email or requests a pizza on the website, data is converted into segments. Segments are passed on different OSI layers and converted into packets. Packets are then converted into frames. Frames are also not transmitted via physical cables; instead, it converted into bits before actual transmission.

Q19. Differentiate Logical Topology from Physical Topology.

Ans: Logical Topology is a network that defined how data is transmitted from source to destination irrespective of the physical connection of devices.

Physical Topology is an actual physical interconnection of cables that are laid down for connectivity.

Q20. What is the role of the LLC sublayer?

Ans: The logical link control (LLC) is the upper sublayer of the data link layer of the OSI model. It provides flow control to the Network layer by using different codes. Error correction is another function of this layer.

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Disclaimer: This tutorial is for educational purpose only. Individual is solely responsible for any illegal act.

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