Cisco | CCNA | Basic Networking | Interview Questions

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  • July 26, 2019
  • CCNACiscoNetworking
Cisco | CCNA | Basic Networking | Interview Questions

Regularly placed Networking Interview Questions:

In today’s fast world, the Internet is so handy that anyone can easily get an answer for any query/question on it. At an earlier time, preparation for an interview was a very big task as he/she needs to go through all the concerned books and materials available carefully. But nowadays the internet has made it so easy.  We can get lots of question-answer sets for different technologies easily on the Internet. So, interview preparation becomes so simple for all with the help of CCNA Course in Pune.

In this blog series from CCNA Classes in Pune, I am going to list the most significant and regularly placed networking interview questions and answers, which will help you to take one step ahead in your successful career. This is the first part of the series where I covered Basic Networking Interview questions and answers.

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Q>1] What is a Network?

Ans:] Network is connecting 2 or more devices with each other using transmission medium for the purpose of sharing information and sharing resources like Printer, Internet Connection, etc.

Q>2] What is the purpose of the Network?

Ans:] There are main two purposes of the Network as below:

  • Sharing information, data, news, etc.
  • Sharing different resources like Printer, Internet Connection, Storage devices – NAS, etc.

Q>3] What is a Node?

Ans:] A node is any device connected in the network, eg. Computer, Laptop, Cell phone, Printer, etc.

Computers are called as workstations, but workstation term cannot use for all devices like Printer, so Node is a common word used for networking devices of any type.

Q>4] What are the different types of Network?

Ans:] According to the geographical area covered, the following are the types of Network:

  • LAN: Local Area Network – Within an office or home, Smallest and Fastest network, easy to manage
  • CAN: Campus Area Network – Within one Campus area, Slower and complex than LAN
  • MAN: Metropolitan Area Network – Within a City, Slower and more complex than CAN
  • WAN: Wide Area Network – Network without boundary, the biggest network in the word – Internet is an example of WAN. Slowest and most complex to manage.
  • PAN: Personal Area Network – Available with Wireless network, ex. Bluetooth

Q>5] What are different casting methods?

Ans:] There are 3 casting methods as below:

  • Unicast: One to one communication
  • Multicast: One too many communication (but not all)
  • Broadcast: One to all communication.

Q>6] What are different transmission methods?

Ans:] Mainly there are two transmission methods: Simplex and Duplex

  • Simplex: One direction communication only. Ex. TV and Radio Broadcast
  • Duplex: Both direction communication.

A duplex method is again divided into two types as Half Duplex and Full Duplex

  • Half Duplex: At a time only in one direction. Ex. Walkie-Talkie
  • Full Duplex: Simultaneously in both the directions. Ex. Cell phone communication

Q>7] What is Network Topology?

Ans:] Network Topology is nothing but the structure or layout or design of your network. Basically there are two types of Topology: Physical Topology and Logical Topology

  • Physical Topology: Actual physical structure of Network
  • Logical Topology: Defines how data will be flow in the Network

Q>8] What are the types of Network Topology?

Ans:] Types of Network physical topology are as below:

  • Bus Topology
  • Ring Topology
  • Star Topology
  • Mesh Topology
  • Tree Topology
  • Hybrid Topology

Q>9] Explain briefly different Network Topologies.

  • Bus Topology: CSMA/CD Technology, always broadcast, More Collisions, Single Point Failure, used in LAN
  • Ring Topology: Token Technology, more waiting time, Single Point Failure, used in LAN
  • Star Topology: CSMA/CD Technology, Central device, Hub – Star-Bus Always Broadcast, Switch – Works on Unicast, Best Topology
  • Mesh Topology: Full Mesh and Partial Mesh, Provides Redundancy, Used in WAN, Expensive
  • Tree Topology: Bus + Star
  • Hybrid Topology: Combo of multiple topologies like Bus, Star, Ring.

Q>10] Differentiate between Domain and Workgroup.

Ans:] Domain

  • Centralized Management
  • Client-Server Topology
  • Need Server permission
  • More secure


  • Distributed Management
  • Peer-to-Peer Topology
  • No Server is there
  • Less Secure

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Q>11] Color code for straight cable and cross-over cable.


Straight Cable Cross-Over Cable
1) White-Orange 1) White-Orange 1) White-Orange 1) White-Green
2) Orange 2) Orange 2) Orange 2) Green
3) White-Green 3) White-Green 3) White-Green 3) White-Orange
4) Blue 4) Blue 4) Blue 4) Blue
5) White-Blue 5) White-Blue 5) White-Blue 5) White-Blue
6) Green 6) Green 6) Green 6) Orange
7) White-brown 7) White-brown 7) White-brown 7) White-brown
8) Brown 8) Brown 8) Brown 8) Brown


Q>12] Which Cable is used to connect Router to PC and Router to Switch?

Ans:]     1) Router to PC: Cross-Over Cable

2) Router to Switch: Straight Cable

Q>13] What is the use of Rollover Cable?

Ans:] Rollover cable is the Console cable which is used to configure the network devices like Router or Switch. It connects Device console port (RJ45) to System’s Serial Port (RS232).

Q>14] Which cable is best for long-distance such as 2 KM or more than this and why?

Ans:] For long-distance such as 2 KM or more than this, the SMF i.e. Single-Mode Fiber Optic Cable is best. As in FOC data is transmitted in the form of Lightwaves, the interference is least in these cables. And in SMF only one light wave is transmitted, so its segment length is more.

Q>15] What is Collision Domain and Broadcast Domain?


  • Collision Domain: When two devices send a packet at the same time on the shared network segment, Collision occurs. A Collision domain is group of nodes i.e. a network where collision can occur.

Hub creates a singles collision domain while Bridge or Switch creates multiple collision domains.

  • Broadcast Domain: Broadcast means one to all communication. A broadcast domain is a network in which a broadcast is forwarded. A broadcast domain is a group of all nodes that can reach each other by using broadcast.

Hub, Bridge, and Switch create a single broadcast domain while Router creates multiple broadcast domains.

Q>16] What are the two types of addresses used in network communication?

Ans:] Two addresses used in network communication are IP address and MAC address.

  • MAC Address: This is the physical address of a node. MAC address is unique and cannot change. It is 48 bits in length and written in Hexadecimal numbers. It works on Data Link Layer (2nd layer of OSI Model). The devices Bridge and Switch work on PDU called Frame using MAC address.
  • IP Address: This is the logical address of a node. The IP address can be changed. It is 32 bits in length and written in Decimal numbers. It works on Network Layer (3rd layer of OSI Model). The device Router works on PDU called Packet using the IP address.

Q>17] What is the difference between Hub, Switch and Router?

Ans:] Following are main differences between the Hub, Switch and Router:

Hub: Hub is a non-intelligent device which works on the Physical layer of the OSI Model. It is a multiport single link device hence works on always broadcasting. It creates single Collision as well as Broadcast Domain.

Switch: Switch works on MAC address i.e. PDU called Frame which works on Data Link Layer of OSI Model. It is a multiport multilink device. The switch works on unicast using Mac Address Table (MAT) to take filtering and forwarding frame decisions. It divides Collision domain while creates a single Broadcast Domain.

Hub and Switch, both can work in a single network or subnet.

Router: Router provides WAN connectivity, means it connects two or more different networks. It works on IP address i.e. PDU called Packet which works on Network Layer of OSI Model. Router divides both the Collision as well as Broadcast Domain.

Q>18] Which MAC address will be entering in the MAT by Switch?

Ans:] Switch will be entering the MAC address of Source in the received frame on the particular port in its MAT i.e. MAC Address Table.

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Q>19] What is Routing?

Ans:] Routing is transmitting data from one network to another network through different networks using the best available path or route.

Q>20] What if Gateway and Firewall?

Gateway: Gateway is a device which is an entrance and exit point of your network. The router is worked as a gateway of the network.

Firewall: Firewall is a Security device. We can filter inbound and outbound packets of your network by configuring ACL i.e. Access Control List on the firewall.

Q>21] What is the OSI Model?

Ans:] OSI i.e. Open System Interconnect Model is a communication Model defined by ISO – International Organization for Standardization. It defines the communication process between nodes in the network. It is an only a theoretical conceptual model which describes the communication process.

Q>22] What are the layers of the OSI Model?

Ans:] The layers of the OSI Model are as below:

  • Physical Layer
  • Data Link Layer
  • Network Layer
  • Transport Layer
  • Session layer
  • Presentation layer
  • Application Layer


Q>23] Which layer in the OSI Model is not working in the LAN communication? Why?

Ans:] Network Layer in the OSI Model is not working in the LAN communication. On the Network layer, Router is working to provide routing which is not required in LAN i.e. in a single network.

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Q>24] Define the devices work on different OSI Layers.

Ans:] Devices works on OSI Layers:

  • Physical Layer: Repeater, Hub, Cables
  • Data Link Layer: Lan Card (NIC), Layer 2 Switches, Bridge
  • Network Layer: Router, Layer 3 Switches
  • Transport Layer: Gateway, Firewall
  • Session layer: Gateway, Firewall
  • Presentation layer: Gateway, Firewall
  • Application Layer: Gateway, Firewall, All End devices like PC, Laptop

Q>25] Define Encapsulation and Decapsulation process.

Ans:] Encapsulation: In communication, at the source/sender end, each layer adds its identity called Header with the data. This process is known as Encapsulation process.

Decapsulation: In communication, at the destination/receiver end, each layer removes its identity called Header from the data. This process is known as Decapsulation process.

Q>26] Define PDU formats sequence during Encapsulation and Decapsulation in OSI Model.

Encapsulation   Decapsulation
PDU Source/Sender Source/Sender PDU
Data Application Layer Application Layer Data
Data Presentation Layer Presentation Layer Data
Data Session Layer Session Layer Data
Segment Transport Layer Transport Layer Segment
Packet Network Layer Network Layer Packet
Frame Data Link Layer Data Link Layer Frame
Bits Physical Layer Physical Layer Bits


Q>27] What are the identities added in PDUs Segment, Packet, and Frame?

Ans:] Following are the identities added in PDUs Segment, Packet, and Frame:

Segment: Source and Destination Service Port Number

Packet: Source and Destination node IP address

Frame: Source and Destination node MAC address

Q>28] During the communication in WAN, which PDU format keeps on changing and which PDU format remains unchanged?

Ans:] During the communication in WAN, Frame PDU format with Source and Destination MAC address keeps on changing while Packet PDU format with Source and Destination IP address remains unchanged.

Q.29] Compare OSI Model and TCP/IP Model.


OSI – ISO TCP/IP – DoD – Department of Defence
7 Application Upper/SW Layers 4 Application
6 Presentation
5 Session
4 Transport Heart of OSI 3 Host-to-Host
3 Network Media/HW Layers 2 Internet
2 Data Link 1 Network Access
1 Physical


Q>30] Why Transport layer is called Heart of OSI Model?

Ans:] Transport layer is the true host to host layer, known as Heart of OSI Model. Following are the important responsibilities of the Transport layer:

  • End-To-End Communication
  • Service Port Addressing
  • Error Control using Sequence number
  • Multiplexing and Demultiplexing using Service Port numbers.
  • Segmentation and reassembly of Segments.
  • Error Recovery
  • Connection Control: Connection-Oriented – TCP, Connectionless – UDP

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Q>31] What is Protocol?

Ans:] Protocol is the set of rules used in network communication.

Q>32] Define TCP/IP Protocol Suite.


TCP/IP Model Protocols
Host-to-Host TCP, UDP, SAMBA, SMB
Internet IP, IPsec, ICMP, IGMP, ARP, RARP
Network Access Proprietary Protocols – Ethernet, Frame Relay, ATM, Token Ring


Q>33] Define Service Port Numbers for different Application layer services.


Service Name Protocol Port Number
FTP – File Transfer Protocol TCP 20, 21
SFTP – Secure FTP TCP 22
TFTP – Trivial FTP UDP 69
HTTP – HyperText Transfer Protocol TCP 80
HTTPS – HTTP Secure TCP 443
SMTP – Simple Mail Transfer Protocol TCP 25
POP3 – Post Office Protocol version 3 TCP 110
IMAP4 – Internet Message Access Protocol version 4 TCP 143
DHCP – Dynamic Host Configuration Protocol UDP 67(S), 68(C)
DNS – Domain Name Service TCP, UDP 53
NTP – Network Time Protocol UDP 123
NNTP – Network News Transfer Protocol TCP 119
RDP – Remote Desktop Protocol TCP, UDP 3389
TELNET – Teletype Network TCP 23
SNMP – Simple Network Management Protocol UDP 161


Q>34] Difference between TCP and UDP.


*TCP – Transmission Control Protocol *UDP – User Datagram Protocol
Connection-oriented Protocol. Connection-less Protocol.
Establish a connection before sending data. Do not establish connection.
Take Acknowledgement. Do not take acknowledgement.
Secure Protocol. Less secure Protocol.
Slow Fast


Q>35] Difference between ARP and RARP.

ARP – Address Resolution Protocol: ARP resolves MAC address from IP address OR resolves IP to MAC address. This is used by systems to resolves destination node MAC address to form a PDU Frame.

RARP – Reverse ARP: RARP resolves IP address from MAC address OR resolves MAC to IP address. This is used by client systems in DHCP environment to get automatic dynamic IP address for their MAC address.

With this I am concluding this blog for Basic Networking. Will meet soon with new part of this blog series within CCNA Training in Pune which will include questions-answers on IP addressing, Subnetting and Route summarization.

All the Best for your Bright future in Networking!!!!!!!!!!!!!!!!!

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