CCNA Interview Questions

A list of top frequently asked CCNA interview questions and answers are given below.

1) What is the difference between switch and hub?

Switch

Switches are used at data link layer.

Switches create separate collision domain and a single broadcast domain.

Address learning

Forward/filter decision using mac address.

Hub

Hubs are used at physical layer.

Hubs create single collision domain and a single broadcast domain.

No addressing.

No filtering.

2) What is the difference between Switch and Router?

Switch

Switch is a device that filters and forwards packets between LAN segments.

Switches are used at data link layer or sometimes the network layer of OSI model and support any packet protocol.

Switches contains multiple collision domains and have a single broadcast domain.

Router

Router is a device that forwards data packets along network.

A router is connected to at least two networks, commonly two LANs or WANs and its ISPs network.

In network, a router can have at least two broadcast domains.

3) What are the advantages of using Switches?

Switches are used to receive a signal and create a frame out of the bits from that signal. The signals enable you to get access and read the destination address and after reading that it forward that frame to appropriate frame. So, switches are very important part of transmission.

4) What is Routing?

Routing is a process of finding a path to transfer data from source to destination.

5) What are Routers?

The process of routing is done by the devices known as Routers. Routers are the network layer devices.

6) What is the advantage of VLAN?

VLAN facilitates you to create a collision domain by groups other than just physical location while in conventional LAN domains are always tied to physical location.

7) What is HDLC?

HDLC stands for High Level Data Link Control protocol. It is property protocol of Cisco which is the default encapsulation operated with Cisco routers.

8) What are the advantages of LAN switching?

Following are the main advantages of LAN switching:

• It allows full duplex data transmission and reception.
• Media rate adaption.
• Easy and efficient migration.

9) What is DLCI?

DLCI stands for Data Link Connection Identifiers. These are normally assigned by a frame relay service provider in order to uniquely identify each virtual circuit that exists on the network.

10) What are the different types of networks?

These are the two major types of networks:

• Peer-to-Peer Network
• Server-based Network

11) What is the difference between private IP and public IP?

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

12) What is the difference among straight cable, cross cable and rollover cable?

Straight cable: Straight cable is used to connect different group devices. For example: Switch- Router.

Cross cable: Cross cable is used to connect same group devices. For example: Switch-Switch.

Rollover cable: Rollover cable is used to connect console port to computer.

13) What is the difference between tracert and traceroute?

Both tracert and traceroute commands are used to do the same work. The only diffence is that traceroute command is used on a router or switch while the tracert command is used on pc.

14) Explain the terms Unicast, Multicast, Broadcast and Multicast.

• Unicast: It specifies one to one communication.
• Multicast: It specifies one to a group communication.
• Broadcast: It specifies one to all communication.
• Multicast: It specifies one to nearest communication.

15) What is the difference between cross cable and straight cable?

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

For example: If you want to connect one PC to another PC, you have to use cross cable while, to connect one switch to a router, you have to use straight cable.

16) What is the difference between static IP addressing and dynamic IP addressing?

• Static IP addresses are reserved and they don't change over time while dynamic IP addresses can be changed each time you connect to the internet.
• Static IP addresses are given manually while dynamic IP addresses are provided by DHCP server.

17) What is the difference between CSMA/CD and CSMA/CA?

CSMA/CD stands for Carrier Sense Multiple Access with Collision Detection. It is a media access control method used in local area networking using early Ethernet technology to overcome the occurred collision.

CSMA/CA stands for Carrier Sense Multiple Access with Collision Avoidance. It is used in wireless network to avoid collision.

18) What is the purpose of Data Link Layer?

The main purpose of data link layer is to check that whether messages are sent to the right devices. Another function of data link layer is framing.

19) What is VLAN?

VLAN stands for Virtual Local Area Network.

20) What is subnet? Why is it used?

Subnets are used in IP network to break up larger network into smaller network. It is used to optimize the performance of network because it reduces traffic by breaking the larger network into smaller networks. It is also used to identify and isolate network's problem and simplify them.

21) What is the difference between communication and transmission?

Communication is a process of sending and receiving data by an externally connected data cable whereas transmission is a process of sending data from source to destination.

22) What is Topology in CCNA?

Topology is an arrangement of various elements (links, nodes etc.) of computer network in a specific order. These are the different types of topology used in CCNA:

• Bus
• Star
• Ring
• Mesh
• Tree
• Hybrid etc.

23) What is the passive topology in CCNA?

When the topology enables the computers on the network only to simply listen and receive the signals, it is known as passive topology because they don't amplify the signals any way.

24) What is RAID in CCNA?

RAID is a method which is used to standardize and categorize fault-tolerant disk systems. RAID levels provide various facilities like performance, cost, reliability etc. These three are the mostly used RAID levels:

• Level 0: (Striping)
• Level 1: (Mirroring)
• Level 5: (Striping and Parity)

25) What is the point-to-point protocol in CCNA?

Point-to-point protocol is an industry standard suite of protocols which uses point-to-point link to transport multiprotocol datagram.

26) What are the possible ways of data transmission in CCNA?

These are the three possible ways of data transmission:

• Simplex
• Half-duplex
• Full-duplex

27) What are the protocol data units (PDU) in CCNA?

Protocol data units (PDU) are the minimum possible units used at different layers of the OSI model to transport data.

Layers PDU

Transport Segments

Network Packets/Datagrams

Data-link Frames

Physical Bits

28) What is the difference between RIP and IGRP?

RIP depends on number of hops to determine the best route to the network while, IGRP considers many factors before decides the best route to take i.e. bandwidth, reliability, MTU and hops count.

29) What are the different memories used in a CISCO router?

Three types of memories are used in a CISCO router:

• NVRAM: It is used to store the startup configuration file.
• DRAM: It stores the configuration file that is being executed.
• Flash Memory: It is used to store the system IOS.

30) What is the difference between full-duplex and half-duplex?

Although both are the communication devices and both are used to transmit and receive data but full-duplex facilitate you to transmit and receive data at the same time while half-duplex cannot receive while it is transmitting data.

31) What is BootP?

BootP is a short form of Boot Program. It is a protocol that is used to boot diskless workstation connected to the network. BootP is also used by diskless workstations to determine its own IP address and also the IP addresses of server PC.

32) What is a Frame Relay?

Frame Relay is used to provide connection oriented communication by creating and maintaining virtual circuits. It is a WAN protocol that is operated at the Data Link and physical layer to maintain high performance rating.

33) What is Latency?

Latency is the amount of time delay. It is measured as the time difference between at the point of time when a network receives the data and the time it is sent by another network.

34) What is MAC address?

MAC address stands for Media Access Control address. This is an address of a device which is identified as the Media Access Control Layer in the network architecture. The MAC address is unique and usually stored in ROM.

35) What is the difference between ARP and RARP?

ARP stands for Address Resolution Protocol. ARP is a protocol that is used to map an IP address to a physical machine address.

RAPR stands for Reverse Address Resolution Protocol. RARP is a protocol that is used to map a MAC address to IP address.

36) What is the size of an IP address?

The size for IPv4 is 32 bits and 128 bits for IPv6.

37) What is Ping? What is the usage of Ping?

PING stands for Packet Internet Groper. It is computer network tool which is used to test whether a particular host is reachable across an IP address or not.

38) What is checksum?

Checksum is a simple error detection scheme in which each transmitted message is accompanied by a numerical value based on the number of set bits in the message.

39) What are the different types of password used in securing a Cisco router?

There are five types of passwords can be set on a Cisco router:

• Consol
• Aux
• VTY
• Enable Password
• Enable Secret

40) What is the usage of Service Password Encryption?

Service Password Encryption command is used to encrypt all passwords on your router to hide from your running config.