You’ve earned your CCNA certification. Congratulations! Now it’s time to put your networking skills to use in real life. When applying or interviewing for networking jobs, you’ll probably answer a number of questions similar to those found on the CCNA exam. Boning up on what you’ve learned before your interview will help increase your confidence and successfully convey your knowledge to a prospective employer.

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In addition to CCNA-oriented interview questions, be prepared for some questions regarding how your technical knowledge relates to the position you’re applying for, along with how well you work in a team environment. Most network engineers work with other engineers, IT administrators, and development and operations (DevOps) personnel to support the entire system.

Here are some of the top CCNA questions you might encounter when you go for your next job interview.  

1. What is networking?

Don’t be surprised if you have to answer this basic question. Networking is the process of creating and using wired or wireless networks for exchanging information and electronic communication such as files.

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2. What are data packets?

Data packets are the encapsulation units that transmit information across a network. A data packet contains the sender’s information, the recipient’s information, and the data contained. It also contains the numeric identification number that defines the order and packet number. When you send data across the network, that information segments into data packets. The recipient then puts these packets together to be able to read the information. Basically, data packets contain the information and routing configurations for your transferred message.

3. What is a node?

A node is a connection point on the network for transmitting data. As the name suggests, a node is the connection point on the network for the transmission of data. The node can be a printer, computer, or any device that can send and receive data over the network.

4. What is routing? 

Fundamentally, routing is the movement or transfer of information across a network (intra or inter) from a source to a destination. Routers do the routing. These network layer devices have a routing table that sends network traffic from one location to another location or segment on the network.

Routers reduce network traffic compared to regular hubs. When a user sends network traffic across the network, a hub broadcasts to all segments of the network. With a router, the device analyzes the TCP/IP packet, sees the destination location, and then uses its lookup table to route the packet to the right network segment and destination. Switches also route traffic in a similar fashion.

5. What does protocol mean?

A protocol is the rule used to connect two or more devices to transfer information from one device to another. Protocols also define how data transfer from one network to another network.

6. How is RIP different from IGRP?

Routing Information Protocol (RIP) uses hop count to determine the best route to a remote network within a single autonomous system. Cisco developed the Interior Gateway Routing Protocol (IGRP) to provide a more robust option for routing within an autonomous system. Before determining the best route, IGRP factors in conditions such as bandwidth, MTU, and reliability in addition to hop count.

7. What does MTU stand for?

MTU stands for maximum transmission unit. It’s the maximum packet size that will send across the network without requiring fragmentation. When you configure a router, a default MTU sets. You can increase MTUs across the network, but this setting generally slows down the network compared to smaller MTU settings. Some network applications require larger MTU sizes, and that’s when you need to configure MTU sizes on your routers manually.

8. Define bandwidth in terms of network architecture

While the term bandwidth is thrown around for most basic networking speeds and capacity, bandwidth is technically the data capacity of a network. It measures the volume of data for a transmission connection. Bandwidth measures in kilobits per second or Kbps.

9. What are the two types of networks defined in the CCNA?

Peer-to-peer network and server-based network.

10. What is 100BaseFX?

It’s a version of Fast Ethernet that uses fiber-optic cable as the main transmission medium for wiring campus backbones. 100 stands for data speed in Mbps.

11. How do unicast, multicast, and broadcast differ?

Unicast refers to one-to-one communication. Multicast refers to one-to-group (many) communication. Broadcast refers to one-to-all communication.

12. What’s the difference between full duplex and half duplex?

In full duplex, the device that’s transmitting and the device that’s receiving can communicate together. That is, communication can take place in both directions at the same time. In half duplex, a device can’t transmit while it’s receiving and vice versa. Communication takes place in only one direction.

13. What’s the difference between a hub, a router, and a switch?

A hub is a network hardware device that connects multiple Ethernet devices together, making them act as a single network segment. A hub works at Layer 1 (physical layer) of the OSI model and supports a single collision domain and a single broadcast domain.

A router is a networking gateway device that forwards data packets to computer networks. At least a single LAN connects a router with its IP address or with LAN or WAN. It supports two broadcast domains. Routers are sometimes confused with hubs, modems, or even switches; however, routers can combine the functions of these components and connect with these devices to improve Internet access or help create business networks.

A switch is networking hardware that connects devices on a computer network by using packet switching to receive and forward data to the destination device. It forwards the packets between various LAN segments. It’s the platform for packet control when data sends at Layer 2 (data link layer) or Layer 3 (network layer) of the OSI model. A switch supports a single broadcast domain and multiple collision domains.

A switch connects multiple devices to create a network. A router connects multiple switches and their respective networks to form a larger network.

14. What’s the difference between broadcast domain and collision domain?

A broadcast domain contains all the devices on a specific network segment that can reach each other through Ethernet broadcasts. Broadcasts sent by a device in one broadcast domain cannot forward to devices in another broadcast domain. This separation improves network performance because not all devices on a network will receive and process broadcasts.

All ports on a router are in different broadcast domains, while all ports on a hub or switch are in the same broadcast domain.

A collision domain is a part of the network where packet collisions can occur, or when two devices on a shared network segment send packets simultaneously. Colliding packets must be discarded and resent, reducing network efficiency.

In a hub environment, all devices connected to the hub are in the same collision domain. In contrast to hubs, every port on a router or switch is in a separate collision domain, effectively eliminating the possibility of collisions.

15. What are the layers of the OSI model?

Seven layers comprise the OSI model:

16. What’s the function of the application layer in the OSI model?

The application layer is what developers and engineers use to send traffic across the network. This layer supports the communication components of applications and provides network services in the application process. This layer is especially important for synchronizing software between servers and client machines.

17. What’s the difference between user mode and privileged mode on a Cisco router?

When you’re using a Cisco router, user mode enables the user to perform routine tasks such as viewing the router status and basic system information and connecting to remote devices. In privileged mode, the user can perform all tasks enabled in user mode and a lot more; this includes making router configuration changes, debugging, viewing all status messages and errors, and making various tests. Network administrators use privileged mode.

18. What are the different memories used in a Cisco router?

19. What’s an IP address?

Each device that wants to communicate with other devices on a TCP/IP network needs an IP address. An IP address is software-based (logical), which differs from a hardware-based MAC address assigned to a network interface controller (NIC). The IP address uniquely identifies the host (computer, printer, router, etc.) on a TCP/IP network.

20. What’s the size of an IPv4 address versus IPv6?

An IPv4 address is 32 bits. An IPv6 address is 128 bits.

21. What’s the difference between static and dynamic IP addresses?

Static IP addresses don’t change over time and are reserved statically. Dynamic IP addresses change every time a device connects to the Internet.

22. How do private IP addresses differ from public IP addresses?

You use Public IP addresses when you have to route data globally over the Internet. They grant internet access to websites and companies. Once connected to the Internet, the public IP addresses become unique worldwide. On the other hand, private IP addresses are for personal and local use. You cannot route them over the internet. Private IP addresses can be the same in different organizations.

23. What is PoE?

An IEEE standard, PoE stands for Power over Ethernet. It’s the technology that enables electric power to pass to network devices over the existing data connection (Ethernet).

24. What is subnetting?

A widely used practice in network management, subnetting involves breaking up a network into sections through addressing. Several interconnected networks are created under a single address space, viewing each section as a sub-network, or subnet, rather than a collection of independent networks. Once the network splits up into sections, an IP address should allocate to each device in a subnet. Your subnetting address allocation divides up the available range of addresses into a range reserved for each subnet.

You accomplish subnetting by manipulating the subnet mask, which divides the IP address for the subnet into a network prefix and host identifier. Subnetting helps alleviate network congestion.

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25. Is it better to add a network segment to a growing network or continue to use the same subnet mask?

Growing networks start to suffer from network congestion. When you segment the network, routers are better able to route traffic to specific parts of the network without broadcasting signals across only one segment. When you reduce broadcasting, you lower congestion, which speeds up your network. With an extensive growing network, it’s better to start segmenting the network and create subnet masks for different segments.

26. What is network segmentation?

Network segmentation enables administrators to control the flow of traffic between subnets based on granular policies. Segmentation divides a network into individual segments, generally through the use of virtual LANs (VLANs). Most often, organizations use segmentation to improve network visibility and monitoring, boost performance, isolate network problems faster, reduce congestion, and increase security. Segmentation makes it easier to detect and respond to an unknown intrusion in the network.

27. What causes network congestion?

With all of the streaming applications and peer-to-peer software, network congestion is common on a large network. Network congestion occurs when applications send more data than the network devices (e.g., routers and switches) can accommodate. Too many people are trying to use limited bandwidth simultaneously. Most companies have a limited amount of bandwidth they can use before they pay extra, which is why companies limit bandwidth by blocking streaming and peer-to-peer applications using firewalls.

28. What is network latency?

Latency is the term used to describe delays in communication over a network. Latency usually measures as a round-trip delay, or the time it takes for information (data, voice, or video) to reach its destination in the network and back again. Latency is affected by bandwidth speeds, network card performance, cabling, and congestion. If latency is too high, an application may “time out,” resulting in poor user experience.

These questions give you a good idea of how to prepare for a CCNA interview. The pool of CCNA certified professionals is large and will continue to grow. Give yourself an edge by refreshing your knowledge of the basic terms, techniques, and best practices you learned while earning your CCNA credential. You don’t have to know all the answers to the questions that may come your way. Just enough to leave a memorable impression.

Page Last Updated: November 2021

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