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Top 30 CCNA Interview Questions


1)    What is Routing?

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 the purpose of the Data Link?

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

3)    What is the key advantage of using switches?

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.

4)    When does network congestion occur?

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.

5)    What is a Window in networking terms?

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

6)    Does a bridge divide a network into smaller segments?

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

7)    Which LAN switching method is used in CISCO Catalyst 5000?

This model uses the Store-and-forward switching method. It stores the entire frame to its buffers and performs a crc check before deciding whether or not to forward that data frame.

8 ) What is the role of the LLC sublayer?

The LLC sublayer, short for Logical Link Control, can provide optional services to an application developer. One option is to provide flow control to the Network layer by using stop/start codes. The LLC can also provide error correction.

9)    How does RIP differ from IGRP?

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.

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

-    NVRAM stores the startup configuration file
-    DRAM stores the configuration file that is being executed
-    Flash Memory - stores the Cisco IOS.

11)    What is BootP?

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.

12)    What is the function of the Application Layer in networking?

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.

13)    Differentiate User Mode from Privileged Mode

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.

14)    What is 100BaseFX?

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.

15)    Differentiate full-duplex from half-duplex.

In full-duplex, both the transmitting device and the receiving device can communicate simultaneously, that is, both can be transmitting and receiving at the same time. In the case of half-duplex, a device cannot receive while it is transmitting, and vice versa.

16)    What is MTU?

MTU stands for Maximum Transmission Unit. It refers to the maximum packet size that can be sent out onto the data line without the need to fragment it.

17)    How does cut-through LAN switching work?

In Cut-Through LAN switching, as soon as the router receives the data frame, it will immediately send it out again and forward it to the next network segment after reading the destination address.

18)    What is latency?

Latency is the amount of time delay that measures the point from which a network device receives a data frame to the time it sends it out again towards another network segment.

19)    Utilizing RIP, what is the limit when it comes to number of hops?

The maximum limit is 15 hop counts. Anything higher than 15 indicates that the network is considered unreachable.

20)    What is a Frame Relay?

Frame Relay is a WAN protocol that provides connection-oriented communication by creating and maintaining virtual circuits. It has a high performance rating and operates at the Data Link and Physical Layers.

21)    How do you configure a Cisco router to route IPX?

The initial thing to do is to enable IPX routing by using the "ipx routing" command. Each interface that is used in the IPX network is then configured with a network number and encapsulation method.

22)    What are the different IPX access lists?

There are two access lists: Standard and Extended. Standard Access List can only filter the source or destination IP address. An Extended Access List uses the source and destination IP addresses, port, socket and protocol when filtering a network.

23)    Explain the benefits of VLANs.

VLANs allow the creation of collision domains by groups other than just physical location. Using VLANs, it is possible to establish networks by different means, such as by function, type of hardware, protocol, among others. This is a big advantage when compared to conventional LANs wherein collision domains are always tied to physical location.

24)    What is subnetting?

Subnetting is the process of creating smaller networks from a big parent network. Being a part of a network, each subnet is assigned some additional parameters or identifier to indicate its subnet number.

25)    What are the advantages of a layered model in the networking industry?

A layered network offers many advantages. It allows administrators to make changes in one layer without the need to make changes in the other layers. Specialization is encouraged, allowing the network industry to make progress faster. A layered model also lets administrators troubleshoot problems more efficiently.

26)    Why is UDP lease favored when compared to TCP?

It's because UDP is unreliable and unsequenced. It is not capable of establishing virtual circuits and acknowledgements.

27)    What are some standards supported by the Presentation layer?

Presentation layer supports many standards, which ensures that data is presented correctly. These include PICT, TIFF and JPEG for graphics, MIDI, MPEG and QuickTime for Video/Audio.

28)    What's the simplest way to remotely configure a router?

In cases when you need to configure a router remotely, the most convenient is to use the Cisco AutoInstall Procedure. However, the router must be connected to the WAN or LAN through one of the interfaces.

29)    What does the show protocol display?

-    routed protocols that is configured on the router
-    the address assigned on each interface
-    the encapsulation method that was configured on each interface

30)    How do you depict an IP address?

It can be done in three possible ways:
-    using Dotted-decimal. For example:
- using Binary. For example: 10000010.00111011.01110010.01110011
-    using Hexadecimal. For example: 82 1E 10 A1

Network Administrator Preparation Questions

Question # 1
Who is network administrator?
Network administrator is responsible for the maintenance of computer hardware and software systems that make up a computer network including the maintenance and monitoring of active data network or converged infrastructure and related network equipment.
Network administrators are generally mid-level support staff within an organization and do not typically get involved directly with users. Network administrators focus on network components within a company's LAN/WAN infrastructure ensuring integrity. Depending on the company and its size, the network administrator may also design and deploy networks.

Question # 2
What is network management?
Network management is the operation, administration, maintenance, and provisioning (OAMP) of networked systems. Network management is essential to command and control practices and is generally carried out of a network operations center.

Question # 3
List the layers of the OSI reference model?
There are 7 OSI reference layers:
*    Physical Layer
*    Data Link Layer
*    Network Layer
*    Transport Layer
*    Session Layer
*    Presentation Layer
*    Application Layer

Question # 4
Explain routers?
Routers can connect two or more network segments. These are intelligent network devices that store information in its routing table such as paths, hops and bottlenecks. With this info, they are able to determine the best path for data transfer. Routers operate at the OSI Network Layer.

Question # 5
Describe point to point link?
Anonymous FTP is a way of granting user access to files in public servers. Users that are allowed access to data in these servers do not need to identify themselves, but instead log in as an anonymous guest.

Question # 6
What is link?

A link refers to the connectivity between two devices. It includes the type of cables and protocols used in order for one device to be able to communicate with the other.

Question # 7
Explain backbone network?
A backbone network is a centralized infrastructure that is designed to distribute different routes and data to various networks. It also handles management of bandwidth and various channels.

Question # 8
Define LAN?
LAN is short for Local Area Network. It refers to the connection between computers and other network devices that are located within a small physical location.

Question # 9
Define node?
A node refers to a point or joint where a connection takes place. It can be computer or device that is part of a network. Two or more nodes are needed in order to form a network connection.

Question # 10
Explain subnet mask?
A subnet mask is combined with an IP address in order to identify two parts: the extended network address and the host address. Like an IP address, a subnet mask is made up of 32 bits.

Question # 11
Explain the maximum length allowed for a UTP cable?
A single segment of UTP cable has an allowable length of 90 to 100 meters. This limitation can be overcome by using repeaters and switches.

Question # 12
What can be considered as good passwords?
Good passwords are made up of not just letters, but by combining letters and numbers. A password that combines uppercase and lowercase letters is favorable than one that uses all upper case or all lower case letters. Passwords must be not words that can easily be guessed by hackers, such as dates, names, favorites, etc. Longer passwords are also better than short ones.

Question # 13
Define the number of network IDs in a class C network?
For a Class C network, the number of usable Network ID bits is 21. The number of possible network IDs is 2 raised to 21 or 2,097,152. The number of host IDs per network ID is 2 raised to 8 minus 2, or 254.

Question # 14
Tell me what happens when you use cables longer than the prescribed length?
Cables that are too long would result in signal loss. This means that data transmission and reception would be affected, because the signal degrades over length.

Question # 15
What common software problems can lead to network defects?
Software related problems can be any or a combination of the following:

*    Client server problems
*    Application conflicts
*    Error in configuration
*    Protocol mismatch
*    Security issues
*    User policy and rights issues

Question # 16
Tell me which protocol can be applied when you want to transfer files between different platforms, such between UNIX systems and Windows servers?
Use FTP (File Transfer Protocol) for file transfers between such different servers. This is possible because FTP is platform independent.

Question # 17
Explain the use of a default gateway?
Default gateways provide means for the local networks to connect to the external network. The default gateway for connecting to the external network is usually the address of the external router port.

Question # 18
Define the proper termination rate for UTP cables?
The proper termination for unshielded twisted pair network cable is 100 ohms.

Question # 19
Explain netstat?
Netstat is a command line utility program. It provides useful information about the current TCP/IP settings of a connection.

Question # 20
What is ping?
Ping is a utility program that allows you to check connectivity between network devices on the network. You can ping a device by using its IP address or device name, such as a computer name.

Question # 21
Define peer to peer?
Peer to peer are networks that does not reply on a server. All PCs on this network act as individual workstations.

Question # 22
Tell me what advantages does fiber optics have over other media?
One major advantage of fiber optics is that is it less susceptible to electrical interference. It also supports higher bandwidth, meaning more data can be transmitted and received. Signal degrading is also very minimal over long distances.

Question # 23
Can you please explain the difference between hub and a switch?
A hub acts as a multi-port repeater. However, as more and more devices connect to it, it would not be able to efficiently manage the volume of traffic that passes through it. A switch provides a better alternative that can improve the performance especially when high traffic volume is expected across all ports.

Question # 24
Explain DNS?

DNS is Domain Name System. The main function of this network service is to provide host names to TCP/IP address resolution.

Question # 25
List the different network protocols that are supported by Windows RRAS services?
There are three main network protocols supported: NetBEUI, TCP/IP, and IPX.

Question # 26
How maximum networks and hosts are in a class A, B and C network?
1)    For Class A, there are 126 possible networks and 16,777,214 hosts
2)    For Class B, there are 16,384 possible networks and 65,534 hosts
3)    For Class C, there are 2,097,152 possible networks and 254 hosts

Question # 27
What is the standard color sequence of a straight-through cable?
Orange/white, orange, green/white, blue, blue/white, green, brown/white, brown.

Question # 28
Tell me what protocols fall under the application layer of the TCP/IP stack?
Following are the protocols under TCP/IP Application layer: FTP, TFTP, Telnet and SMTP.

Question # 29
Is it possible to connect two computers for file sharing without using a hub or router?
Yes, you can connect two computers together using only one cable. A crossover type cable can be use in this scenario. In this setup, the data transmit pin of one cable is connected to the data receive pin of the other cable, and vice versa.

Question # 30
Define ipconfig?
Ipconfig is a utility program that is commonly used to identify the addresses information of a computer on a network. It can show the physical address as well as the IP address.

Question # 31
Can you please explain the difference between straight-through and crossover cable?
A straight-through cable is used to connect computers to a switch, hub or router. A crossover cable is used to connect two similar devices together, such as a PC to PC or Hub to hub.

Question # 32
Explain client/server?
Client/server is a type of network wherein one or more computers act as servers. Servers provide a centralized repository of resources such as printers and files. Clients refers to workstation that access the server.

Question # 33
What is networking?

Networking refers to the inter connection between computers and peripherals for data communication. Networking can be done using wired cabling or through wireless link.

Question # 34
Suppose when you move the NIC cards from one PC to another PC, does the MAC address gets transferred as well?
Yes, that's because MAC addresses are hard-wired into the NIC circuitry, not the PC. This also means that a PC can have a different MAC address when the NIC card was replace by another one.

Question # 35
What is clustering support?
Clustering support refers to the ability of a network operating system to connect multiple servers in a fault-tolerant group. The main purpose of this is the in the event that one server fails, all processing will continue on with the next server in the cluster.

Question # 36
Suppose if a network which contains two servers and twenty workstations, where is the best place to install an Anti-virus program?
An anti-virus program must be installed on all servers and workstations to ensure protection. That's because individual users can access any workstation and introduce a computer virus when plugging in their removable hard drives or flash drives.

Question # 37
What is Ethernet?
Ethernet is one of the popular networking technologies used these days. It was developed during the early 1970s and is based on specifications as stated in the IEEE. Ethernet is used in local area networks.

Question # 38
Give some drawbacks of implementing a ring topology?
In case one workstation on the network suffers a malfunction, it can bring down the entire network. Another drawback is that when there are adjustments and reconfiguration's needed to be performed on a particular part of the network, the entire network has to be temporarily brought down as well.

Question # 39
Can you please explain the difference between CSMA/CD and CSMA/CA?
CSMA/CD, or Collision Detect, retransmits data frames whenever a collision occurred. CSMA/CA, or Collision Avoidance, will first broadcast intent to send prior to data transmission.

Question # 40
What is SMTP?
SMTP is short for Simple Mail Transfer Protocol. This protocol deals with all Internal mail, and provides the necessary mail delivery services on the TCP/IP protocol stack.

Question # 41
Define multicast routing?
Multicast routing is a targeted form of broadcasting that sends message to a selected group of user, instead of sending it to all users on a subnet.

Question # 42
Explain the importance of encryption on a network?

Encryption is the process of translating information into a code that is unreadable by the user. It is then translated back or decrypted back to its normal readable format using a secret key or password. Encryption help ensure that information that is intercepted halfway would remain unreadable because the user has to have the correct password or key for it.

Question # 43
How are IP addresses arranged and displayed?
IP addresses are displayed as a series of four decimal numbers that are separated by period or dots. Another term for this arrangement is the dotted decimal format.  An example is

Question # 44
Explain the importance of authentication?
Authentication is the process of verifying a user's credentials before he can log into the network. It is normally performed using a username and password. This provides a secure means of limiting the access from unwanted intruders on the network.

Question # 45
What is tunnel mode?
This is a mode of data exchange wherein two communicating computers do not use IPSec themselves. Instead, the gateway that is connecting their LANs to the  transit network creates a virtual tunnel that uses the IPSec protocol to secure all communication that passes through it.

CCNA Interview Questions III

64.    On which base switches take decisions?


Mac Address

65.    How ARP brings MAC address for switch?


Through Broadcast

66.    How many collision domains are in switch?


Equal number of ports

67.    How many broadcast domains are in Switch?

Ans. One

68.    What is the subnetmask of / 27 in network based and host based?


In network based 224 { 128+64+32}and in host based 248 (128+64+64+16+8)

69.    What will be the prefix length of 224 in VLSM?


27 (carry 3 bits from host (128+64+16=224) and add in network ports (24+3=27)

70.    How many valid IP will b in /21 in route Summarization?

Ans. 1044

71.    In which protocol you manually enable route summarization?



72.    In which protocol supenetting is enable by default?



73.    What is MAC address size of IPv6?

Ans. 64 bits

74.    Default Packet Size of IPv6?


8 Bytes = 16*8 =128 bit

75.    How many fillers we can put in one IP of IPv6?


ONE (:: called filler)

76.    Which mathematically form used inIPv6?

Ans. Hexadecimal

77.    What is quality of IPv6?


a)    Router processing will rapid because field size wills 8 bytes (but in IPv4 it was 12 byres)

b)    No Fragmentation

c)    No Checksum

78.    Define Network?


Communication, Resource sharing and Media (When multiple host share their resources with each other OR when multiple devices connect with each other for resource sharing )

79.    Explain Types of communication in IPv4?


Unicast, Multicast and Broad cast

80.    Types of communication in IPv6 ?


Unicast, Multicast and Anycast

81.    Types of Resource Sharing?


INTRANET   , Extranet and Internet .

82.    What is Collision?


When signal hits each other, collision accord.

83.    Which Type of Transmission Bus Topology Support?


Half Duplex

84.    What is the difference between half duplex and full duplex?


In half duplex, sender should b one. In full duplex, sender can be multiple.

85.    Which way of communication bus topology use?

Ans. Broadcast

86.    If there is only 2 Host in Bus Topology is that possible collision accord?


Yes, because end terminal will not absorb signals. Signal will be bounce back and collision will accord.

87.    HUB in Star topology or Bus Topology?


In star topology, but logically works like a bus topology.

88.    What we called 64 Bit Mac­address in IPV6?


EUI= Enhanced universal identifier – 16 bits add in IPv6 so it’s called EUI

89.    What is loop back IP in IPV6?


1 and ping 6

90.    Which command we use for ping in IPv6?


Ping6 source IP ­s Destination IP

91.    How many types of router?


Two types

i)    Modular

ii)    Non­Modular

92.    When we use Router?


For communication between different networks

93.    Which works router Do?


1­ Path selection and

2­ Packet Switching {frame relay}

94.    What cable called V.35?


Serial Connectivity cable

95.    How many types of Ethernet?


4 types

i)    Ethernet

ii)    Fast Ethernet

iii)    Gigabit

iv)    10 Giga.

96.    Which cable called roll­over?


Console access able

97.    Which cable we connect in DB­9?


Roll over calbe

98.    How many ways to access router?


3 ways

i)    Telnet (IP)

ii)    AUX (Telephone)

iii)    Console (cable)

99.    What is IOS?


Internet Operating system. Its router’s operating system.

100.    Which mode called privilege mode?


Second mode

CCNA Interview Questions II

1.    What is difference between Switch & Hub?
Answer : Switch:
Switches operate at Layer 2 Data Link Layer
Address Learning
Forward / Filter decision using MAC address Loop Avoidance
Breakup collision domains
Switches create separate collision domains but a single broadcast domain

Hub operates at Layer 1 Physical Layer No Filtering
No Addressing
Hub creates single collision domain and single broadcast domain Make forwarding to all the ports when signal is arrived

2.    What is PING utility?
Answer :

PING – Packet Internet Gopher
A utility that verifies connections to one or more remote hosts. The ping command uses the ICMP echo request and echo reply packets to determine whether a particular IP system on a network is functional. Ping is useful for diagnosing IP network or router failures.

3.    What is a VLAN? What does VLAN provide?

Answer :

VLAN – Virtual Local Area Network
Vlan is a logical grouping or segmenting a network connected to administratively defined ports on a switch, they provide Broadcast control, Security and Flexibility.

4.    What is Subnetting? Why is it used?

Answer :

Used in IP Networks to break up larger networks into smaller subnetworks. It is used to reduce network traffic, Optimized network performance, and simplify management i.e. to identify and isolate network problems.

5.    Difference between the Communication and Transmission?

Answer :

Communication is the process of sending and receiving data by means of a data cable that is connected externally.
Transmission means the transfer of data from the source to the destination.

6.    What is RAID in ccna?

Answer :

A method used to standardize and categorize fau    ms. RAID

levels provide various mixes of performance, relia    e servers provide three of the RAID levels: Level 0 (striping), Level 1 (mirroring), and Level 5 (striping & parity).

7.    What are 10Base2, 10Base5 and 10BaseT Ethernet LANs?

Answer :

10Base2 an Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband signaling, with a contiguous cable segment length of 200 meters (185mts). Known as Thinnet.

10Base5 an Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband signaling, with a contiguous cable segment length of 500 meters. Known as Thicknet.

10BaseT an Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses two pairs of twisted­pair baseband signaling, with a contiguous cable segment length of 100 meters.

8.    What are the two types of Transmission Technology available in ccna?

Answer :
Two types of Transmission Technology available in ccna are Point – to – Point and Broadcast

9.    What is point­to­point protocol in ccna?

Answer :

An  industry STANDARD SUITE    of protocols for the use of point­to­point links to transport multiprotocol datagrams.

10.    What are the possible ways of data exchange in ccna?

Answer :

Possible ways of data exchange in ccna are Simplex
Half­duplex Full­duplex

11.    What is difference between Baseband and Broadband Transmission in ccna?

Answer :

In a baseband transmission, the entire bandwidth of the cable is consumed by a single signal.

In broadband transmission, signals are sent on multiple frequencies, allowing multiple signals to be sent simultaneously.

12.    What is Protocol Data Unit in ccna?

Answer :

The processes at each layer of the OSI model. Layers­­­­­­­­­­PDU
Transport­­­­­­­Segments Network­­­­­­­­­Packets/Datagrams Data Link­­­­­­­Frames

13.    What are major types of Networks and explain?

Answer :

Peer­to­Peer Network
Computers can act as both servers sharing resources and as clients using the resources.

Server­based Network
Provide centralized control of network resources and rely on server computers to provide security and network administration

14.    What is Passive Topology in ccna?

Answer :

When the computers on the network simply listen and receive the signal, they are referred to as passive because they don’t amplify the signal in any way.

15.    What is the Mesh Network?

Answer :

A network in which there are multiple network links between computers to provide multiple paths for data to travel.

16.    How network Gateway is different from Routers?
Answer : Gateway
A device connected to multiple physical TCP/IP networks capable of routing or delivering IP packets between them.

It’s a layer 3 device that connects 2 different networks and routes packets of data from one network to another. It breaks up Broadcast domain as well as Collision Domain.

17.    What is the network Brouter?

Answer :

It’s a Hybrid device that combines the features of both bridges and routers.

18.    What is the network Subnet?

Answer :

A subnet is the subdivision of an IP network.

19.    What is the Frame relay, in which layer it comes?

Answer :

Frame relay is an industry standard, shared access, switched Data Link Layer encapsulation that services multiple virtual circuits and protocols between connected mechanism.
Frame relay is a packet­switched technology.

20.    What is the Terminal Emulation, in which layer it comes?

Answer :

The use of software, installed on PC or LAN server, that allows the PC to function as if it were dumb terminal directly attached to a particular type of mainframe.
Telnet is also called as terminal emulation. It belongs to application layer.

21.    What is the Beaconing?

Answer :

An FDDI frame or Token Ring frame that points to serious problem with the ring, such as a broken cable. The beacon frame carries the address of the station thought to be down.

22.    What are the NetBIOS and NetBEUI?

Answer :

NetBIOS – Network Basic Input / Output System
An application­programming interface (API) that can be used by programs on a local area network (LAN). NetBIOS provides programs with a uniform set of commands for requesting the lower­level services required to manage names, conduct sessions, and send datagrams between nodes on a network.

NetBEUI – NetBIOS Extended User Interface
An improved version of the NetBIOS protocol, a network protocol native to Microsoft Networking. It is usually used in small, department­size local area networks (LANs) of 1 to 200 clients. It can use Token Ring source routing as its only method of routing.

23.    What is the Cladding?

Answer :

A layer of a glass surrounding the center fiber of glass inside a fiber­optic cable.

24.    What is the Attenuation?

Answer :

In communication weakening or loss of signal energy, typically caused by distance.

25.    What is the MAC address?

Answer :

The address for a device as it is identified at the Media Access Control (MAC) layer in the network architecture. MAC address is usually stored in ROM on the network adapter card and is unique.

26.    What is the ICMP protocol?

Answer :

ICMP – Internet Control Message Protocol
It is a Network Layer Internet protocol, which can report errors and status information. We can use the ping command to send ICMP echo request messages and record the receipt of ICMP echo reply messages. With these messages, we can detect network or host communication failures and troubleshoot common TCP/IP connectivity problems.

27.    What is the difference between ARP and RARP?

Answer :

ARP – Address Resolution Protocol
The protocol that traces IP addresses to MAC addresses.

RARP – Reverse Address Resolution Protocol
The protocol within the TCP/IP stack that maps MAC addresses to IP addresses.

28.    What is the difference between TFTP and FTP application layer protocols?

Answer :

TFTP – Trivial File Transfer Protocol
A stripped down version of FTP, easy to use and fast. TFTP has no Directory browsing, no Authentication and insecure it can only send and receive files.

FTP – File Transfer Protocol
The TCP/IP protocol used for transmitting files between network nodes. FTP allows access to both Directories and files, manipulating directories, typing file contents and copying files between hosts.

29.    Explain 5­4­3 rule?

Answer :

In a Ethernet network, between any two points on the network, there can be no more than five network segments or four repeaters, and of those five segments only three of segments can be populated.

30.    What is the MAU?

Answer :

MAU – Multistation Access Unit

31.    What is the difference between routable and non­ routable protocols?

Answer :

Routable protocols can work with a router and can be used to build large networks. Non­Routable protocols are designed to work on small, local networks and cannot be used with a router.

32.    What is the logical link control?

Answer :

One of two sublayers of the data link layer of OSI reference model, as defined by the IEEE 802 standard. This sublayer is responsible for error detection but not correction, flow control and framing.

33.    What is the Virtual Channel?

Answer :

A logical circuit that is created by Virtual channel links. It carries data between two endpoints in a network.

The other name for Virtual Channel is Virtual Circuit.

34.    What is the Virtual Path?

Answer :

Along any transmission path from a given source to a given destination, a group of virtual circuits can be grouped together into what is called path.

35.    What is the multicast routing?

Answer :

Sending a message to a group multicast address is called multicasting, and its routing algorithm is called multicast routing.

36.    What is the IGP (Interior Gateway Protocol)?

Answer :

Any protocol used by an internetwork to exchange routing data within an autonomous system. E.g. RIP, IGRP and OSPF.

37.    What is OSI?

Answer :

Open System Interconnection. t was first name of 7 Layer

38.    What is the default size of Frame?

Answer :

1518 bytes

39.    Which layer are called upper layer?

Answer :

a)    Application Layer ­ 7
b)    Presentation Layer – 6
c)    Session Layer – 5

40.    Tell me How many reserve ports?

Answer :

0 – 1023

41.    Which decision called socket base?

Answer :

IP plus port (IP on layer 3 and port on Layer 4 – In Encapsulation, socket base decision on Network Layer ­Layer 3)

42.    Do you know How many types of Data?

Answer :

Voice, video, text

43.    What is segmentation and fragmentation?

Answer :

To divide data in pieces is called segmentation and divide segmentation in pieces called Fragmentation.

44.    Which layer called error detection layer?

Answer :

Data link layer

45.    What is FCS?

Answer :

Frame Check Sequence ­
CRC (Cyclic Redundancy Check) algorithm runs in switch that called FCS (Frame Check Sequence)

46.    What is Encapsulation and De­encapsulation?

Answer :

To send data called encapsulation and receive data called De­encapsulation.

47.    What is BIA?

Answer :

Burn in Address other name is MAC address

48.    What is Size of IPv4 MAC Address?

Answer : 48 Bits

49.    Why MAC address called Physical address?

Answer :

Because it’s not changeable

50.    Who controls MAC address uniqueness and how?

Answer :

IEEE (Institute of Electrical Electronics and Engineering) Controls its uniqueness. They divide 48 bits MAC address in two parts. (
First 24 bits part called OUI (Organizational unique identifier) and other 24 bits are device code.

51.    How we can see MAC address from DOS Prompt?

Answer : ipconfig/all

52.    Why IP address called logical address?

Answer :

Private IP called logical address because they are change able.

53.    What is the size of IPV4?

Answer : 32 bits

54.    What is Syntax of IPV4?

Answer : DOT

55.    How many types of IPS?

Answer :

Three Types of IP 1­ Public
2­ Private
3­ Special IP

56.    What are the ranges of private IPS?

Answer :

A Class = –
B Class = –
C Class = –

57.    What is the difference between bus topology and HUB?

Answer :

Hub is Centralized device ( series ) .Bus topology is Decentralized device (in parallel)

58.    Is hub intelligent device?

Answer :

No; because it not use header

59.    Which protocol switch use for filling its MAC­Table?

Answer :

ARP – Address Resolution Protocol

60.    What is CAM?

Answer :

Content Address Memory. its another name of MAC address table.

61.    Which type for communication switch do?

Answer :

In case of any new event switch do broadcast, after that always do Unicast.

62.    If line down and protocol also down; in this case which layer move problem?

Answer :

Physical Layer – Layer 1

63.    If line up, but protocol down which layer should be troubleshot?

Answer :

Data link problem – Layer 2

CCNA Interview Questions

Question 1

Two interface of the router is configured with IP addresses, subnet mask and IP address, subnet mask Would the routing table of the router contain any information? Provide explanations


When the interfaces are configured with the respective IP addresses and subnet mask, the router would perform an ANding operation with the IP address and subnet mask. This would ultimately yield the network address for the interface. Once the interfaces are configured with the IP addresses and subnet masks, two entries

would be available in the routing tables which are (Network address of and (Network address of

Question 2
What is the use of a subnet mask in the routing table of a router? Answer

The subnet mask is used to identify the network address corresponding to the received IP packets on the router. Assume that an IP packet has arrived with the destination IP address as route table contains the following entry. would be “And ed” with and determined that the destination IP address is a member of the network.

Question 3

A router has two paths to a network with a static route and dynamic routing protocol. Which path would a packet bound to the network take when it reaches the router?


When there are two paths to the same network, the path with the lower administrative distance would be used for forwarding the packet. The AD (Administrative Distance) of static route is lower than that of dynamic routing protocols. So the path which the static route points to would be taken by the packet.

Question 4

How is a wild card mask interpreted by a router? Explain with an example.


Take an example where a router has a wild card mask of, which is associated with an IP address The 0 in the wild card mask implies that when a packet is received, the octet corresponding to the value 0 in wild card mask should be verified. In the above example, the three octets corresponding to the 0 in the wild card mask is 192.168.1 and the 255 would imply to ignore the values in the last octet. So this ACL, whether permit or deny, would look for the network address

Question 5

Can an ACL be used to block a DOS based IP spoofing attack from random source addresses?


An ACL can only be used if the source or destination addresses or networks are pre-defined. If the source addresses are random, an ACL would be ineffective in defending against the attack.

Question 6

If ping is blocked on a system using ACL, does it imply that other communication like TCP or UDP is also disallowed on that specific system?


Ping uses ICMP for communication. Blocking ping does not imply that TCP or UDP communication is disallowed, provided the access list allows for the required protocols for communication.

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