CCNA Interview Questions with Answers

This tutorial presents a collection of CCNA interview questions with answers. To help you in preparing for CCNA interview, each interview question is presented with a detailed answer. Learning these CCNA interview questions and answers will definitely help you in facing CCNA job interview more confidently.

This tutorial is the second part of our article “CCNA Job Interview Questions with Answers”. This part provides CCNA interview questions and answers from OSI Layer model. Other parts of this tutorial are available here.

Basic CCNA Networking Interview questions and Answers

This is the first part of this collection. It provides CCNA interview questions with answers from these sections; Network services, Internetworking, Network types, network topology, communication message types, collision domain and broadcast domain.

CCNA interview questions with answers from OSI Layer model.

What does OSI stand for?

OSI stands for Open Systems Interconnection.

What does IOS stand for?

IOS stands for International Organization for Standardization.

What are the OSI and IOS?

OSI is the reference model which describes necessary protocols, standards and technologies in communication between networking devices.

IOS is the international organization who invented the OSI model.

What are the OSI layers?

OSI model describes the complete process of communication between networking devices. This process includes several protocols, standards, terms and technologies. To make this process easy to understand, layer approach is used. An OSI layer is the logical section of OSI model which describes a specific section of OSI model.

How many layers does OSI model have?

There are seven layers in OSI model.

What is the name of OSI layers?

The name of OSI layers are Application, Presentation, Session, Transportation, Network, Data Link and Physical layer. These layers are divided in two categories; upper layers and lower layers.

Upper layers: - Application, Presentation, Session and Transportation

Lower layers: - Network, Data Link and Physical

What are numeric expression forms of OSI Layers?

With standard name, each layer also has a numeric expression form associated with it. Following table lists numeric expression form of each layer.

Standard Name Numeric expression form
Application Layer 7
Presentation Layer 6
Session Layer 5
Transportation Layer 4
Network Layer 3
Data Link Layer 2
Physical Layer 1

What are the network protocols?

Network Protocols are the set of rules and regulations under which networking devices make communication. To make an effective communication, several protocols are used. There are two types of protocol; proprietor protocol and open protocol.

Proprietor protocols are developed, maintained and used by a specific organization or company to make communication between their own networking devices.

Open protocols are developed are maintained by a public organization and used by all to make communication between different vendor’s networking devices.

What are the network standards?

Network standards are the agreed definition of network protocols. A standard defines what and how a protocol functions.

Name any five popular organizations who define network standards.

  1. ANSI (American National Standards Institute)
  2. IEEE (Institute of Electrical and Electronics Engineers)
  3. ISO (International Organization for Standardization)
  4. IETF (Internet Engineering Task Force)
  5. W3C (World Wide Web Consortium)

What is the bottom layer of OSI model?

Physical layer

What layer of the OSI model breaks data stream in smaller segments?

The transport layer breaks data stream in smaller segments.

Which layer defines the standards for network cable?

Physical layer

In which layer do hub, repeater and NIC work?

Hub, repeater and NIC work in layer1 (physical layer).

Which protocol is used to deliver the e-mail?

SMTP

Which protocol is used to receive the e-mail?

POP3 or IMAP

In which layer SMTP, POP3 and IMAP work?

Application layer

Which layer of the OSI model works with packets?

Network layer or layer 3

A network administrator is observing link light of switch for troubleshooting. What layer of OSI model he is troubleshooting?

Link light of switch shows the status of physical link. Physical link is defined in physical layer of OSI model.

Which layer of the OSI model works with frame?

Data link layer or layer 2

Which layer of the OSI model works with binary signal?

Physical layer or layer 1

Which addresses are required to deliver a data packet across the network?

Following addresses are required to deliver a data packet correctly to the destination: -

Port address: - Locate the correct application at destination

IP address: - Locate the correct network and host

MAC address: - Locate the correct node in network

While delivering a packet to the remote network, which is the only address, which changes from its original address and why and where it changes?

If the packet is delivered in remote network, its MAC address or Layer 2 address will be changed. When a packet crosses the router, router updates source MAC address with its own MAC address in packet.

Which address does router use to determine where a packet needs to be delivered?

IP Address

Which transport layer protocol is responsible for unreliable delivery?

User Datagram Protocol (UDP) is responsible for unreliable delivery. UDP protocol does not track whether the data has been received at the destination or not.

Which TCP/IP protocol is responsible for error and status reporting?

Internet Control Message Protocol (ICMP) is responsible for error and status reporting.

In which layer of OSI model, ICMP protocol works?

ICMP protocol works in network layer of the OSI model.

Which field from IP header router uses to find the destination of the packet?

Destination IP address

What flags are set on the second phase of the three-way handshake?

ACK/SYN

What ICMP message type is used for an echo request?

ICMP message type 8 is used for an echo request.

What ICMP message type is used for an echo reply?

ICMP message type 0 is used for an echo reply.

In TCP, which flag indicates a successful transfer of previous packets?

ACK (acknowledgement flag)

Which transport layer protocol is responsible for reliable delivery?

TCP is responsible for reliable delivery.

As a security administrator you want to block all ping messages. What protocol you have to block?

The ping command uses ICMP protocol. In order to block all ping messages, you have to block this protocol.

Which TCP flag is responsible for dropping a connection at any point of the transmission?

A reset flag (RST) is used to drop the TCP connection at any point of the transmission.

Which layer is responsible for checking and determining the availability of communicating partners including necessary resources in making communication?

Application layer

Which layer is responsible for converting data packets in electrical signals?

Physical layer

In which layer does routing take place?

Network layer or layer 3

Which layer formats, presents, encodes and coverts data?

Presentation layer

Which layer creates, manages and terminates the sessions between applications?

Session layer

Which layer uses logical addressing to enable communication between two end devices?

Network layer uses logical addressing to enable communication between end devices.

Which layer defines the cabling standards and data moving across the network?

Physical layer

Which layer provides error detection?

Data Link layer

Which layer uses MAC addresses?

Data Link layer

Which layer keeps the data from different applications separate on the network?

The session layer creates separate session for each application to keep its data separate from other applications.

Which layer is represented by segments?

Transport Layer

Which layer is represented by packets?

Network Layer

Which layer is represented by frames?

Data Link Layer

Which layer is represented by bit and bytes?

Physical layer

Which layer segments and reassembles data?

Transport layer

Which layer transmits the data physically and handles error notification, network topology, and flow control?

Data Link Layer

Which layer provides logical addressing, tracks the location of devices in network and calculates the best path to reach at the destination?

Network layer

What is the correct order of data encapsulation?

Data => Segment => Packet => Frame => Signal

What is the correct order of data de-encapsulation?

Signal=> Frame => Packet => Segment => Data

Acknowledgments, sequencing, and flow control are characteristics of which OSI layer?

Transport Layer

Describe any five functions of transport layer.

  1. It breaks data stream in smaller segments.
  2. It sets up and uses a session connection between sender device and receiver device.
  3. As per requirement, it provides both reliable and unreliable delivery of data across the connection.
  4. It supports connection multiplexing which allows multiple applications to send and receive data simultaneously.
  5. It implements flow control through windowing and ready/not ready signals to ensure that one end doesn’t overflow another one with sending too much data on an ongoing connection.

Which protocol is used for reliable data delivery?

TCP

Which protocol is used for unreliable data delivery?

UDP

What is segmentation?

Segmentation is a transport layer function which breaks large data stream in smaller chunks known as segments.

How windowing works?

In Windowing, a window size is defined before the transmission. Source device sends segments equal to window size and waits for an acknowledgement from destination device. Once acknowledgement is received, next set of segments is transferred. If any segment is lost in any batch, destination device notifies sender device about that in acknowledgement signal. Source device resends the lost segments in next batch.

windowing

What is the connection multiplexing?

Connection multiplexing is a transport layer function which allows multiple applications to send and receive data simultaneously between two end devices.

Which methods transport layer uses for flow control?

For flow control, transport layer uses two methods: -

  1. Read/Not ready signal
  2. Windowing

How does ready/not ready signals flow control method work?

In ready/no ready signals method, when a destination device receives more segments than it can handle, it sends a not ready signal back to source device indicating that it should stop transmitting data temporary. Upon receiving stop request from destination device, sender system pause further transmission. When receiver system is ready for next segments, it sends source device a ready signal. Upon receiving ready signal, source device resumes transmission.

What are the drawbacks or disadvantages of ready/not ready signals method?

There are two major drawbacks or disadvantages of ready/not ready signals method: -

Destination device sends not ready signal when its buffer is already filled up. While signal is on its way to the source device, the source device is still sending segments to the destination device, which the destination device has to drop because there is no space available for them.

Destination device sends ready signal only when all segments from buffer are processed. It must have to wait until source device receives ready signal and sends next segments. This causes a delay in the transfer of segments in each occurrence.

What is the length of an IP address?

32 bit

What is the expression form of an IP address?

Binary and decimal

What is the length of a MAC address?

48 bit

What is the expression form of a MAC address?

Hexadecimal

Which frame uses Ether-Type field to identify the network layer protocol?

IEEE Ethernet Frame

That’s all for this part. In next part we will discuss CCNA interview questions and answers from IP address, Subnetting and VLSM sections. If you like this collection, do forget to share it with your friends.

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