Important Questions for CCNA

Interview Questions For CCNA

Q1. What is a ‘router’?

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

Q2. What is a ‘protocol’ in networking?

Ans. A protocol 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.

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. What is 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 other by broadcast at the data link layer.

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

Q6. What is the size of an IP address?

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

Q7. What is a DLCI?

Ans.  DLCI (Data Link Connection Identifiers) are used to uniquely identify each virtual circuit that exists on the network.

Q8. Name the different types of networks

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

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

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

Q10. What is PoE (Power over Ethernet)?

Ans.  Power over Ethernet (PoE) refers to the technology which allows electric power along with data on Ethernet cabling.

Q11. What is the use of ‘ping’ command?

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

Q12. What is ‘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.

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 are used to connect same group devices while straight cables are used to connect different group devices.

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

Ans.  At data link layer.

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. What is 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 and do not change with time.

Q19. What is ‘subnet’? Why is it used?

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

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

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

1. What is Routing?

Answer: Routing is the process of finding a path on which data can pass from source to destination. Routing is done by a device called routers, which are network layer devices.

2. What is routing on a network?

Answer: This might seem like a basic question, but the interviewer might ask it just to see if you know the basics. Routing is done by routers. Routers have a routing table that send 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.

3. What is 100BaseFX?

Answer: This is Ethernet that makes use of fiber optic cable as the main transmission medium. The 100 stands for 100Mbps, which is the data speed.

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

Answer: 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 a growing large network, it’s better to start segmenting the network and create subnet masks for different segments.

5. What is the purpose of the Data Link?

Answer: The job of the Data Link layer is to check messages are sent to the right device. Another function of this layer is framing.

6. What is network congestion?

Answer: With all of the streaming applications and peer to peer software, network congestion is common on a large network. Network congestion occurs when too many people are trying to use limited bandwidth. 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.

7. Differentiate User Mode from Privileged Mode

Answer: User Mode is used for regular task when using a CISCO router, such as to view system information, connecting to remote devices, and checking the status of the router. On the other hand, privileged mode includes all options that are available for User Mode, plus more. You can use this mode in order to make configurations on the router, including making tests and debugging.

8. What are data packets?

Answer: 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 is segmented 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.

9. What is the key advantage of using switches?

Answer: When a switch receives a signal, it creates a frame out of the bits that was extracted from that signal. With this process, it gains access and reads the destination address, after which it forwards that frame to the appropriate port. This is a very efficient means of data transmission, instead of broadcasting it on all ports.

10. What is the difference between RIP and IGRP?

Answer: When you send traffic on a network, the router (default gateway in Windows computer terminology) determines how to route the traffic. RIP determines where to send the traffic by determining the shortest amount of “hops.” A hop is the next router in the traffic’s path. Each router is considered a hop. With IGRP, several more factors are considered. IGRP takes into consideration the bandwidth availability, MTU, reliability and the amount of hops.

11. What is the function of the Application Layer in networking?

Answer: The Application Layer supports the communication components of an application and provides network services to application processes that span beyond the OSI reference model specifications. It also synchonizes applications on the server and client.

12. Define bandwidth in terms of network architecture

Answer: 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 is measured in kilobits per second or “Kbps.”

13. When does network congestion occur?

Answer: Network congestion occurs when too many users are trying to use the same bandwidth. This is especially true in big networks that do not resort to network segmentation.

14. What is the Application Layer in network connectivity?

Answer: The Application Layer is what your developers and software use to send traffic across the network. The Application Layer is especially important for synchronizing software between the server and the client machine.

15. What is BootP?

Answer: BootP is a protocol that is used to boot diskless workstations that are connected to the network. It is short for Boot Program. Diskless workstations also use BootP in order to determine its own IP address as well as the IP address of the server PC.

16. What is subnetting on your network?

Answer: Subnetting is a way to segment your network into smaller “groups.” Subnetting is accomplished by manipulating the subnet mask, which is distributed to desktop computers and routers. Subnetting allows you to create smaller networks within your network, which then reduces congestion on larger networks.

17. What is a Window in networking terms?

Answer: A Window refers to the number of segments that is allowed to be sent from source to destination before an acknowledgement is sent back.

18. What is the difference between user mode and privileged mode on a Cisco router?

Answer: These two modes are somewhat self-explanatory. The user mode allows the user to view router status and basic system information. With privileged mode access status, the router can be configured and all status messages and errors can be viewed. User mode and privileged mode separates standard users on the network and network administrators who need to not only view router status but also make changes to the router’s configurations.

19. What are the different memories used in a CISCO router?

Answer: NVRAM stores the startup configuration file

DRAM stores the configuration file that is being executed

Flash Memory — stores the Cisco IOS.

20. What is network latency?

Answer: Network latency refers to the performance of one device when it communicates with another. Network latency is affected by bandwidth speeds, network card performance, cabling and congestion. High latency can also mean users won’t be able to properly communication with applications, which will “time out” if latency is too high.

21. Does a bridge divide a network into smaller segments?

Answer: Not really. What a bridge actually does is to take the large network and filter it, without changing the size of the network.

22. What does MTU stand for?

Answer: MTU stands for “Maximum Transmission Unit.” When you configure a router, a default MTU is set. MTU determines the maximum size of a packet that is sent across the network. 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 manually configure MTU sizes on your routers.

23. How does RIP differ from IGRP?

Answer: RIP relies on the number of hops in order to determine the best route to a network. On the other hand, IGRP takes consideration many factors before it decides the best route to take, such as bandwidth, reliability, MTU and hop count.

24. What is the difference between full duplex and half duplex devices?

Answer: A full duplex device is preferable, because a full duplex device can send and receive data packets simultaneously. However, with a half duplex device, the device must finish receiving a message before it can then send a message. This can lead to slower transmission speeds and increase network latency.