Top 46 CCNA Interview Questions and Answers

Are you preparing for a CCNA interview? Check out these common CCNA interview questions to help you ace your interview. From topics like VLANs and routing protocols to subnetting and network security, these questions will test your knowledge and readiness for a career in networking. Don’t miss this opportunity to boost your chances of success!

If you want to succeed in your next CCNA interview, here is a carefully curated list of CCNA interview questions and answers that will come in handy in your preparation. In this blog, we have listed the 45 most frequently asked CCNA interview questions that will help both the freshers and experienced candidates boost their interview preparation.

Top CCNA Interview Questions and Answers

The list of commonly asked interview-related CCNA questions and answers is given below:

Q1. What is a ‘router’?

Ans. A router is a device that forwards data packets along with a network.

Q2. What is a ‘protocol’ in networking?

Ans. A protocol in networking is a set of invisible computer rules that enable two devices to connect and transmit data to one another.

Q3. Differentiate between a switch and a hub.

Ans. Switches are used at the data link layer, while hubs are used at the physical layer.

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Q4. How many layers are there in an OSI reference model? Name them.

Ans. There are 7 layers in an OSI (Open Systems Interconnection) reference model. They are:

1. Physical layer
2. Data link layer
3. Network layer
4. Transport layer
5. Session layer
6. Presentation layer
7. Application layer

Q5. Explain the difference between a ‘broadcast domain’ and a ‘collision domain’.

Ans. A broadcast domain is a logical division of a computer network in which all nodes can reach others by broadcast at the data link layer.

A collision domain is a network section where data packets can collide with one another when sent on a shared medium or through repeaters.

Q6. What is the size of an IP address?

Ans.  32 it for IPv4 and 128 bit for IPv6.

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Q7. What is a DLCI?

Ans.  DLCI (Data Link Connection Identifiers) uniquely identifies each virtual circuit on the network.

Q8. Name different types of networks.

Ans.  There are two types of networks – 1) peer-to-peer and 2) server-based.

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Q9. What is the difference between a ‘half-duplex’ and a ‘full-duplex’ system?

Ans.  In a half-duplex system, communication occurs in only one direction, while in a full-duplex system, communication occurs in both directions.

Q10. What is PoE (Power over Ethernet)?

Ans.  Power over Ethernet (PoE) refers to the technology allowing electric power and data on Ethernet cabling.

Q11. Explain the use of ‘ping’ command.

Ans.  Ping (Packet Internet Groper) is a computer network tool that tests whether a particular host is reachable across an IP network.

Q12. Explain ‘round-trip time’.

Ans.  Round-trip time, or round-trip delay, is the time required for a packet to travel from a specific source to a specific destination and back again.

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Q13. What is the difference between public and private IP?

Ans.  Public IP is used across the internet, while private IP is used within the local LAN.

Q14. What is the difference between ‘cross cable’ and ‘straight cable’?

Ans.  Cross cables connect the same group of devices, while straight cables connect different devices.

Q15. At which layer of OSI does frame relay technology work?

Ans.  At the data link layer.

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Q16. What is the size of a Cisco ping packet?

Ans.  The size of a Ping packet in Cisco by default is 100 bytes.

Q17. How many VTP modes are in a switch? Name them.

Ans.  There are three types of VTP modes. They are – server, client, and transparent.

Q18. Explain the difference between static and dynamic IP addressing.

Ans.  Dynamic IP addresses can change every time a device connects to the internet. Static IP addresses are reserved. They do not change with time.

Q19. What is a ‘subnet’?

Ans.  Subnets are used in IP networks to optimize the performance of a network because it reduces traffic by breaking a large network into smaller networks.

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Q20. What does MTU stand for? What is the default size?

Ans. MTU stands for the maximum transmission unit. The default MTU size is 1500 bytes.

Q21. When does network congestion occur?

Ans. Network congestion happens when applications send more data than the network devices like routers and switches can accommodate. This is a common occurrence when many users try using the same bandwidth.

Q22. What is the LLC sublayer, and what is its function?

Ans. LLC is an abbreviation for Logical Link Control and offers application developers optional services. These options include providing flow control to the network layer using stop/start codes. It also corrects an error in the network.

Q23. What is BootP?

Ans. BootP or Boot Program is a protocol for booting diskless workstations in a network. These diskless workstations use BootP to determine their and a server’s IP addresses.

Q24. What is 100BaseFX?

Ans. 100BaseFX is a version of Fast Ethernet that uses fibre optic cable as the main transmission medium for wiring campus backbones. 100 stands for data speed in Mbps.

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Q25. What is HDLC?

Ans. HDLC stands for High-Level Data-Link Control protocol. It is a popular ISO-standard, bit-oriented Data Link layer protocol for transmitting data. It is applicable for both point-to-point and point-to-multipoint communications.

HDLC organizes data into frames that allow the devices to control the data flow. The frame is transmitted via the network to the destination that verifies its successful arrival. 

Some of the benefits of HDLC are: 

• Supports both half and full-duplex communication.
• Offers full data transparency.
• Offers flexibility, reliability, and efficiency of operation for synchronous data communication.
• Supports both synchronous and asynchronous communication.

Q26. Explain VLAN.

Ans. It is the abbreviation for Virtual Local Area Network. It provides data link connectivity for a subnet.

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Q27. What are the benefits of using VLANs?

Ans. There are three primary benefits of using VLANs, which include –

• Security, reduced number of trunk links
• Reduced costs
• Allows creating collision domains other than physical locations

Q28. What is latency?

Ans. It is the time a data packet takes to move from one designated point to another.

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Q29. Can you tell me which is the second layer of an OSI layer model?

Ans. The data link layer is the second layer of an OSI model.

Q30. What is BOOTP?

Ans. It is the short form of Bootstrap Protocol. BOOTP is a computer networking protocol used in IP networks for automatically assigning an IP address to network devices from a configuration server.

Q31. Tell me the easiest way to configure a router remotely.

Ans. The most popular and easy way to configure a router remotely is using Cisco AutoInstall Procedure. However, it should ensure the router is connected to the WAN or LAN.

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Q32. What is Route Poisoning?

Ans. Route Poisoning is making a route unreachable by inserting a table entry of 16 into it. This is done to prevent the problems of inconsistent updates on a route.

Q33. Name different types of passwords that can be used to secure a CISCO router.

Ans. 5 types of passwords can be used to secure a CISCO router, and these are –

• Console
• Aux
• VTY
• Enable password
• Enable secret

Q34. Why should we use network segmentation to manage a large network?

Ans. Segmenting a network helps to ease network traffic and ensures that users receive high bandwidth at all times.  This translates to better performance, especially for a growing network.

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Q35. Which IP address is used for the loopback address and why?

Ans. 127.0.0.1 is used for the loopback address. A loopback address is a special IP address that a network administrator uses to treat the local machine as a remote machine. It is also used for local testing. Any traffic sent by a computer program on the loopback network is addressed to the same computer.

Q36. In the case of RIP, what route entry will be assigned to a dead or invalid route?

Ans. 16 hops will be assigned to a dead or invalid route in case of RIP.

Q37. Explain the different memories used in a CISCO router.

Ans. The following are the different memories used in a CISCO router: 

1. NVRAM (Non-Volatile Random Access Memory) – It stores the startup configuration file.
2. DRAM (Dynamic Random Access Memory) – It stores the configuration file being executed.
3. ROM (Read Only Memory) – The bootstrap software runs and maintains instructions for POST diagnostics.
4. Flash Memory – It stores the Cisco IOS.

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Q38. What is the difference between User Mode from Privileged Mode?

Ans. The differences between User Mode from Privileged Mode are: 

User Mode	Privileged Mode
It is used for the regular task while using a Cisco router.	Offers a lot of options, including those available in User mode.
It lets you view system information, connect to remote devices, check the router’s status, and more.	It allows users to make router configurations, such as tests and debugging.

Q39. What is CDP? Explains its functions.

Ans. CDP stands for Cisco Discovery Protocol. It is a Layer 2 proprietary protocol that runs on Cisco devices, including routers and switches. This protocol collects information about directly connected neighbouring devices. 

It discovers the nearby devices, identifies how they are configured, and enables the systems to learn about each other by using different network-layer protocols. CDP simplifies the process of keeping an up-to-date inventory of Cisco network devices.

The CDP finds out the following information:

• iOS version running on Cisco devices
• IP addresses 
• The hardware platform of devices
• Interface details
• Hostname
• VTP domain
• Duplex setting
• Native VLAN

Q40. How does TCP (Transmission Control Protocol) differ from UDP (User Datagram Protocol)?

Ans. The difference between TCP and UDP are: 

TCP (Transmission Control Protocol)	UDP (User Datagram Protocol)
It is a connection-oriented protocol.	It is a connectionless protocol.
The connection should be established before the data is transmitted over the network.	It sends the data without checking whether the system is ready to receive it.
Delivery of data to the destination router is guaranteed. The server will request the lost part if the connection is lost during transferring files.	It doesn’t guarantee the delivery of data to the destination.
The message will be delivered in the order it is sent.	The message may not be delivered in the same order.
It doesn’t support broadcasting.	It supports broadcasting.
Data is read as a stream. When one packet ends, another begins.	Data Packets are transmitted individually.
The header size is 20 bytes.	The header size is 8 bytes.
It is slower than UDP	UDP is faster and more efficient than TCP
This protocol is mainly used where a secure communication process is required. Example: web browsing and e-mail.	This protocol is used when fast communication is required. Example: VoIP, video, and music streaming.

Q41. What are the different classes of IP addresses? Mention their ranges.

Ans. There are five classes of IP address:

Class	Range
A	1-126
B	127-191
C	192-223
D	224-239
E	240-254

Q42. How to choose DR in OSPF?

Ans. Below are the different ways to choose DR in OSPF:

• Highest priority
• Highest router ID
• Highest IP address

Q43. Which command is used if router IOS is stuck?

Ans. If router IOS is stuck, we use the Ctrl+Shift+F6 and X commands.

Q44. Explain the types of routes available in routers.

Ans. There are three types of routing including dynamic routing, default routing and static routing. These are as follows:

• Static route is also known as non-adaptive route. It is either directly configured on active interface of router or it is added to routing table by administrator.
• Default route is configured to send all packets towards single router. It does not matter if it belongs to a specific network. Such nodes are used when the network deals with single exit point.
• Dynamic route is also known as adaptive route, it makes automatic adjustments of routes as per current state of route on routing table. It uses routing protocols for finding network destinations.

Q45. What is LAN switching? What are its benefits?

Ans. LAN Switching is a form of packet switching used in Local Area Networks. It is a vital component of most networks and helps improve LAN’s overall efficiency and address the existing bandwidth issues. It enables multiple users to communicate directly with each other. LAN switching creates a system of simultaneous, point-to-point connections between pairs of devices. It provides a collision-free network and high-speed networking.

The following are the benefits of LAN Switching: 

• Increased network scalability
• Improved bandwidth performance
• Multiple simultaneous connections
• Reduced congestion and transmission delay
• No single point of failure
• Full-duplex data transmission
• Improved manageability and security

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Q46. Explain the terms Unicast, Multicast, Broadcast

Ans. In all these three terms, ‘cast’ refers to transmitting data packets from the client to the recipient over the communication channel.

1. Unicast (One-to-One):

It is a one-to-one communication technique in which data communication occurs between a single sender and a single recipient in the network.

Examples of Unicast are: 

• Browsing a website. The web server is the sender, and your computer is the receiver.
• Downloading a file from an FTP Server. FTP Server is the sender, and your computer is the receiver.

2. Broadcast (One-to-All):

It specifies one to all communication. Data communication takes place among all the devices available in the network. The data is sent from one computer once and a copy of that data will be forwarded to all the connected devices. Two types of Broadcast are Limited Broadcasting and Direct Broadcasting.

Example of Broadcast: 

• Television networks for video and audio distribution.

3. Multicast (One-to-Many):

Multicast specifies one to group or one to many communication. In Multicast, one or more senders and one or more recipients participate in data transfer. IP multicast traffic is sent to a group and only members of that group receive the Multicast traffic. It uses IGMP (Internet Group Management Protocol) protocol to identify the group. 

Examples of Multicast:

• Sending an e-mail to a particular mailing group.

So, these are some of the most important CCNA interview questions. We hope this blog will help you ace your next CCNA interview.