CCNA Interview Questions and Answers


CCNA stands for Cisco Certified Network Associate. CCNA is a certificate that is given by Cisco Systems. Cisco is one of the major players enjoying monopolies in the fields of information technology, networking, and communication technologies. CCNA certification exams and interviews test an individual’s knowledge of networking. Thus, acquiring a CCNA certification means that the individual is well-versed in networking and networking-related topics. CCNA is a PT certification for any individual looking to establish a career in the field of networking. Hence, obtaining a CCNA certification is a masterstroke and a career booster for any IT job seeker and IT graduate. We have curated some of the best and most frequently asked questions and answers for the CCNA interview. These questions cover various criteria, like aptitude, problem-solving, technicality, etc. These questions are sure to give you a great advantage over other candidates in any CCNA interview.

CCNA interview questions and answers

What are the various networking topics covered in the CCNA program?

The following are the various topics covered under the CCNA program:

  • Network Fundamentals: This includes understanding the basics of networking, including the OSI model, TCP/IP protocols, and IP addressing.
  • Routing and Switching: This includes configuring and troubleshooting routers and switches and understanding routing protocols like OSPF and EIGRP.
  • WAN Technologies: Knowledge of Wide Area Network (WAN) technologies, such as PPP, Frame Relay, and VPNs.
  • Network Security: This is about understanding network security principles, including securing router switches, implementing Access Control Lists (ACLs), and basic security protocols.
  • Automation and Programmability: Introduction to basic network programmability and automation using tools like Python and understanding software-defined networking (SDN).

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What do you mean by the OSI model?

OSI stands for open systems interconnection. The OSI model serves as a conceptual framework, establishing a standardized structure for the functions of telecommunications or computing systems across seven abstraction layers. Developed by the International Organization for Standardization (ISO), its primary purpose is to streamline communication among diverse systems and devices, fostering interoperability in network communication. Within the OSI model, each layer has designated functions, and the interaction between these layers is meticulously defined, ensuring a systematic and well-coordinated approach to communication in networks.

Explain the layers in the OSI model.

The OSI model comprises seven layers arranged from the bottom to the top:

  • Physical Layer (Layer 1): Addressing the physical connections between devices, this layer defines hardware elements like cables, connectors, and electrical signals.
  • Data Link Layer (Layer 2): Responsible for establishing a dependable link between directly connected nodes, the data link layer addresses errors occurring at the physical layer. It consists of two sub-layers: Logical Link Control (LLC) and Media Access Control (MAC).
  • Network Layer (Layer 3): Managing routing, addressing, and logical addressing, the network layer determines the optimal path for data packets to traverse across multiple networks.
  • Transport Layer (Layer 4): Ensuring end-to-end communication, the transport layer is accountable for error recovery, flow control, and the retransmission of lost or corrupted data.
  • Session Layer (Layer 5): Responsible for establishing, managing, and terminating communication sessions between applications, the session layer offers services such as dialog control, token management, and synchronization.
  • Presentation Layer (Layer 6): Focused on the syntax and semantics of exchanged data between systems, this layer translates data between the application layer and lower layers, ensuring compatibility across various data formats.
  • Application Layer (Layer 7): Positioned at the top, the application layer directly engages with end-user services. It furnishes a network interface to software applications and network services, facilitating communication between diverse applications.

What do you mean by data packets? (CCNA basic interview questions)

Data packets function as encapsulation units for transmitting information throughout a network. Within a data packet, you’ll find details about the sender and recipient, along with the actual data. Additionally, it includes a numerical identification number specifying the packet order and number. Whenever data is sent over the network, it undergoes segmentation into these data packets. The recipient’s task involves assembling these packets to comprehend the transmitted information. In essence, data packets encapsulate both the information and rpouting configurations essential for the successful conveyance of your message.

What do you mean by networking?. Also, explain its elements and applications.

Networking encompasses the practice of linking computers and various devices to exchange resources and information. This involves establishing communication links between diverse devices, enabling seamless data exchange and communication. The primary objective of networking is to streamline and enhance efficient communication, collaboration, and the sharing of resources among interconnected devices.

Essential elements of networking involve:

  • Communication: Networking facilitates communication between devices, whether they are situated in close proximity or separated by significant distances. This communication can occur through either wired or wireless connections.
  • Resource Sharing: Devices within a network can share resources such as files, printers, and internet connections. This collaborative sharing enhances efficiency and teamwork within groups or organizations.
  • Data Transfer: Networks enable the transfer of data between devices in various forms, including emails, file transfers, streaming media, and more.
  • Collaboration: Networking supports collaboration by allowing multiple users to collaborate on shared documents, projects, or applications. This is especially vital in business settings where teams collaborate on projects.
  • Internet Connectivity: Networking is a foundational element of internet connectivity, enabling devices to connect to the internet, access online resources, and communicate globally with servers and other devices.
  • Security: Networking involves implementing security measures to safeguard data and systems from unauthorized access. This encompasses the use of firewalls, encryption, and various security protocols.


Networking can occur on a local scale, such as within a home or office (local area network, or LAN), or on a global scale, connecting networks across different geographical locations (wide area network, or WAN). The internet itself forms a vast global network connecting millions of devices worldwide. Various networking technologies and protocols, including TCP/IP, Ethernet, and Wi-Fi, play pivotal roles in establishing and maintaining these connections.

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What is the difference between a hub, router, and switch?

A network comprises various devices that serve distinct functions in facilitating communication. Hubs, routers, and switches are fundamental components, each operating at different layers of the OSI model.

  • Hub:

A hub acts as a basic networking device, functioning at the physical layer (Layer 1). It connects multiple Ethernet devices, creating a single network segment. Hubs lack intelligence and broadcast data to all connected devices, leading to potential network congestion and inefficiency.

  • Router:

Routers, operating at the Network Layer (Layer 3), are networking gateway devices that forward data packets between computer networks. They make intelligent routing decisions based on IP addresses, maintaining routing tables to determine optimal routes. Routers support segmentation, dividing networks into subnets for enhanced efficiency and security. They also serve as gateways connecting local networks to the internet.

  • Switch:

Switches operate at the Data Link Layer (Layer 2) and play a crucial role in forwarding data based on MAC addresses. Unlike hubs, switches learn the MAC addresses of connected devices, enabling them to send data only to the intended recipient. This reduces network congestion and enhances efficiency. Switches support network segmentation, similar to routers, improving overall performance.

In summary, hubs, routers, and switches are integral to network functionality, each serving specific roles in ensuring effective communication and resource sharing. Hubs connect devices at the physical layer, routers handle intelligent routing decisions at the network layer and switches efficiently forward data based on MAC addresses at the data link layer. Together, these devices form the building blocks of robust and well-organized computer networks.

What is the difference between a full duplex and a half duplex? (CCNA interview questions and answers)

In a full-duplex setup, the transmitting device and the receiving device can communicate simultaneously, allowing for bidirectional communication. This means that information can be exchanged in both directions concurrently. Conversely, in a half-duplex configuration, a device is unable to transmit while simultaneously receiving, and vice versa. In this mode, communication occurs in only one direction at any given time.

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What is HDLC? (CCNA interview questions)

HDLC, which stands for High-Level Data Link Control, encompasses a set of communication protocols designed to reliably deliver data frames over communication or network links. Specifically associated with Cisco, it serves as the default encapsulation protocol within Cisco routers. HDLC is proprietary to Cisco and is instrumental in ensuring the accurate and error-free transmission of data. Furthermore, it can offer both connection-oriented and connectionless services.

Explain the concept of subnetting.

Subnetting involves the division of a larger parent network into smaller networks. Each subnet, being a component of the overall network, receives specific additional parameters or identifiers to denote its unique subnet number.

Explain CDP. (CCNA questions and answers)

CDP, which stands for “Cisco Discovery Protocol,” functions as a layer 2 protocol operating at the Media Access Control (MAC) address level. It serves the purpose of identifying port numbers, iOS details, router models, device IDs, and switch models.

How to configure a router remotely? (CCNA aptitude questions and answers)

When there is a necessity to configure a router remotely, the most convenient approach is to utilize the Cisco AutoInstall Procedure. However, the router needs to be connected to the WAN or LAN through one of its interfaces.

Define MTU.

The Maximum Transmission Unit (MTU) establishes the maximum packet size that can be sent as a singular entity in a network connection. This parameter determines the volume of data, measured in bytes, that can be transmitted across a network.

Explain route-poisoning (CCNA basic interview questions for freshers).

Route poisoning is a method employed in computer networking, especially within routing algorithms, to forestall the emergence of routing loops and uphold the stability and efficiency of the network. In route poisoning, a router notifies its neighboring routers about the unavailability of a route by assigning an infinite metric or cost to that particular route.

The mechanism of route poisoning operates as follows:

  • Detection of Route Failure: Upon detecting that a route to a destination network has either failed or is no longer valid, a router promptly updates its routing table to reflect the failure.
  • Infinite Metric Assignment: To communicate the unavailability of the route, the router disseminates information about the failed route to its neighboring routers, assigning an infinite metric. This metric is commonly represented by the maximum possible value or a designated special value, indicating that the route is now unreachable.
  • Propagation: The router with the failed route communicates this information to its neighboring routers, signaling that the specific route is no longer feasible. Neighboring routers, upon receipt of this information, adjust their own routing tables accordingly.

Through the strategic use of an infinite metric, routers can swiftly alert each other about the unavailability of a route, thwarting the development of routing loops. Routing loops, if left unchecked, can lead to the suboptimal utilization of network resources and a substantial decline in network performance. Route poisoning finds widespread application in distance-vector routing protocols such as RIP (Routing Information Protocol) to fortify the stability of routing tables in dynamic network environments.

What is routing?

Routing is the process of guiding data packets between diverse networks or nodes, ensuring their effective delivery to the intended destination. Within computer networking, routing encompasses decision-making regarding the most optimal paths for data to traverse from the source to the destination within an intricate network of routers.

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What are the different aspects of routing? 

The following are the different aspects of routing:

  • Path Determination: Routing algorithms are employed by routers to ascertain the most suitable path for data packets to reach their intended destinations. These algorithms take into account factors like network topology, link costs, and available bandwidth.
  • Packet Forwarding: Upon establishing the optimal path, routers facilitate the forwarding of data packets along the chosen route. Each router scrutinizes the destination address in the packet header and makes decisions based on its routing table.
  • Dynamic Adaptation: Routing frequently involves dynamic processes, with routers continuously updating their routing tables to adapt to changes in network conditions. This dynamic adaptation is indispensable for addressing network failures, shifts in traffic patterns, or the addition or removal of network nodes.
  • Routing Protocols: Routing protocols encompass sets of rules and conventions enabling routers to communicate and share pertinent information about the network. Examples of routing protocols include RIP (Routing Information Protocol), OSPF (Open Shortest Path First), and BGP (Border Gateway Protocol).
  • Internet Routing: On a global scale, the Border Gateway Protocol (BGP) serves as a prevalent tool for overseeing routing between autonomous systems—large networks managed by diverse organizations or service providers.
  • Static vs. Dynamic Routing: Routing options include both static and dynamic approaches. In static routing, administrators manually configure routing tables, specifying paths for data packets. Conversely, dynamic routing involves routers exchanging information and dynamically updating routing tables based on prevailing network conditions.