Best 50+ CCNA Interview Questions & Answers [95% SUCCESS]
Last updated on 16th Jun 2020, Blog, Interview Questions
CCNA is a continuously varying field which needs the students as well as professionals to upgrade their skills with the new features and knowledge, to get fit for the jobs associated. Over thousands of vacancies available for the CCNA developers, experts must be acquainted with all the components of CCNA technologies. This is necessary for the students in order to have in-depth knowledge of the subject so that they can have better employment opportunities in the future. According to one study, most of the companies and businesses have moved to the CCNA. Now, you cannot predict how huge the future is going to be for the people experienced in the related technologies.
Hence, if you are looking for boosting up your profile and securing your future, CCNA will help you in reaching the zenith of your career. Apart from this, you would also have a lot of opportunities as a fresher. A list of top 100 frequently asked CCNA interview questions and answers are given below.
1. What is Routing?
- Routing is a process of finding a path to transfer data from source to destination.
- Routing can be performed in a variety of networks such as circuit switched networks and computer networks.
- In packet switching networks, routing makes a decision that directs the packets from source to the destination.
- Routing makes use of a routing table, which maintains the routes of various destinations.
Types of routing:
- Static routing: Static routing is a routing technique where an administrator manually adds the routes in a routing table. Static routes are used when the route selections are limited. Static routes can also be used in those situations where the devices are fewer and no need to change in the route configuration in future.
- Dynamic routing: Dynamic routing is a routing technique where protocols automatically update the information of a routing table.
2. What are Routers?
- The devices known as Routers do the process of routing. Routers are the network layer devices.
- The router is a networking device which is used to transfer the data across the networks, and that can be wired or wireless.
- Routers use headers and routing tables to determine the best route for forwarding the packets.
- Router analyzes the data which is being sent over the network, changes how it is packaged and sends it over the network.
Examples of routers are:
- Brouter: Brouter stands for “Bridge Router”. It serves both as a router and bridge.
- Core router: Core router is a router in the computer network that routes the data within a network, but not between the networks.
- Edge router: An edge router is a router that resides at the boundary of a network.
- Virtual router: A virtual router is a software-based router. The virtual router performs the packet routing functionality through a software application. A Virtual Router Redundancy protocol implements the virtual router to increase the reliability of the network.
- Wireless router: A wireless router is a router that connects the local networks with another local network.
3. 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.
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 PING utility? Ans. 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.
6. What is a VLAN? What does VLAN provide?
VLAN: Virtual Local Area Network
Vlan is a logical grouping or segmenting of a network connected to administratively defined ports on a switch, they provide Broadcast control, Security and Flexibility.
7. What is Subnetting? Why is it used?
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.
8. Difference between the Communication and Transmission?
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.
9. What is RAID in ccna?
A method used to standardize and categorize fault-tolerant disk systems. RAID levels provide various mixes of performance, reliability, and cost. Some servers provide three of the RAID levels: Level 0 (striping), Level 1 (mirroring), and Level 5 (striping & parity).
10. Which layer of the OSI model is responsible for reliable connections?
The Transport layer of the OSI model is responsible for reliable connections.
11. What is the difference between acknowledgments and handshaking?
Handshaking is used to negotiate the properties of a connection that is being established. Acknowledgments are used to tell the sender that data has been successfully received by the destination during the use of a connection.
12. What is the difference between private IP and public IP?
Public IP is used across the internet while private IP is used within the local LAN.
13. What are 10Base2, 10Base5 and 10BaseT Ethernet LANs?
- 10Base2 is 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 is 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 is an Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses two pairs of twisted-pair baseband signaling, with a contiguous cable segment length of 100 meters.
14. What are the two types of Transmission Technology available in ccna?
Two types of Transmission Technology available in ccna are Point – to – Point and Broadcast
15. What is HSRP?
HSRP, or the Hot Standby Routing Protocol, is a Cisco proprietary protocol that brings routing functionality to end devices that would otherwise not be capable of taking advantage of redundant network connections. HSRP enables a pair of Cisco routers to work together to present the appearance of a single virtual default-gateway to end devices on a LAN segment.
16. What does AAA stand for?
Authentication, authorization, and accounting
17. The H.323 protocol is used for what?
H.323 is used for multi service (multimedia) applications, usually in a Voice Over IP environment.
18. What type of routing protocol maintains neighbors?
19. What is the range of values for administrative distance?
20. Describe the difference between unicast, multi cast, and broadcast traffic?
- Unicast traffic flows from a single source to a single destination MAC address.
- Multicast traffic flows from a single source MAC address to many destinations and uses a functional MAC address.
- Broadcast traffic is from a single source to all devices on the Ethernet segment. This is specified by a destination MAC address of all ones.
21. What is the difference between tracert and traceroute?
Both tracert and traceroute commands are used to do the same work. The only difference is that traceroute command is used on a router or switch while the tracert command is used on pc.
22. 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.
23. 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 a cross cable while, to connect one switch to a router, you have to use a straight cable.
24. What is the difference between Baseband and Broadband Transmission in ccna?
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.
25. What is the Protocol Data Unit in ccna?
The processes at each layer of the OSI model:
- Layers: PDU
- Transpose: Segments
- Network: Packets/Datagrams
- Data Link: Frames
- Physical: Bits
26. What is Passive Topology in ccna?
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.
27. What is the Mesh Network?
A network in which there are multiple network links between computers to provide multiple paths for data to travel.
28. What is the network Brouter?
It’s a Hybrid device that combines the features of both bridges and routers.
29. What is distance vector? Explain with an example.
Distance Vector Protocols send periodic updates every 30 secs or at some time interval to the adjacent routers.In case if there is a link failure immediately,they inform you to update only after 30 secs. For example, RIP routing information protocol is a distance vector protocol. Here distance indicates length between two routers and vector means in which link direction the link is connected between them.
30. What is the Frame relay, in which layer it comes?
Frame relay is an industry standard, shared access, switched Data Link Layer encapsulation that services multiple virtual circuits and protocols between connected mechanisms. Frame relay is a packet-switched technology.
31. Mention what is the metric of EIGRP protocol?
EIGRP protocol consists of:
- Maximum Transmission Unit
32. Mention what does the clock rate do?
Clock Rate enables the routers or DCE equipment to communicate appropriately.
33. Mention what command you must use if you want to delete or remove the configuration data that is stored in the NVRAM?
Erase startup- coding is the command you must use if you want to delete the configuration data that is stored in the NVRAM
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34. What is the difference between RIP and IGRP?
Following are the differences between RIP and IGRP:
|Basis of Comparison||RIP||IGRP|
|Full form||RIP stands for routing information protocol.||IGRP stands for interior gateway routing protocol||Description||RIP is a distance vector-based routing protocol||IGRP is a distance vector based interior gateway
|Determination of route||RIP depends on the number of hops to determine the
best route to the network.
|IGRP considers many factors before deciding the best
route to take, i.e., bandwidth, reliability, MTU and hops count.
|Standard||RIP is an industry standard dynamic protocol.||IGRP is a Cisco standard dynamic protocol|
|Organization used||RIP is mainly used for smaller sized organizations||IGRP is mainly used for medium to large-sized
|Maximum routers||It supports a maximum of 15 routers||It supports a maximum of 255 routers|
|Symbol used||RIP is denoted by ‘R’ in the routing table||IGRP is denoted by ‘I’ in the routing table|
|Administrative distance||The administrative distance of RIP is 120||The administrative distance of IGRP is 100|
|Algorithm||RIP works on Bellman ford Algorithm||IGRP works on Bellman Ford Algorithm|
35. 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:
- Enable Password
- Enable Secret
36. Which feature should a routing protocol have to support VLSM?
It should include a subnet mask of each destination address.
37. What are the three sources of signal degradation on a data link?
The three sources of signal degradation on a data link are attenuation, interference, and distortion. Attenuation is a function of the resistance of the medium. Interference is a function of noise entering the medium. Distortion is a function of the reactive characteristics of the medium, which react differently to different frequency components of the signal.
38. What is the difference between a RIP Request message and a RIP Response message?
A Request message asks a router for an update. A Response message is an update.
39. Which two types of Request messages does RIP use?
A Request message may either ask for a full update or in some special cases it may ask for specific routes.
40. Under what circumstances will a RIP response be sent?
A Response is sent when the update timer expires, or upon reception of a Request message.
41. Why does RIP hide subnets at major network boundaries?
RIP updates do not include the subnet mask of the destination address, so a RIP router depends on the subnet masks of its own interfaces to determine how an attached major network address is subnetted. If a router does not have an attachment to a particular major network address, it has no way to know how that major network is subnetted. Therefore, no subnets of a major network address can be advertised into another major network.
42. Which UDP port number is used to access IGRP?
IGRP does not use a UDP port. It is accessed directly from the network layer, as protocol number 9.
43. What is the Terminal Emulation, in which layer it comes?
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 terminal emulation. It belongs to the application layer.
44. What is the Beaconing?
An FDDI frame or Token Ring frame that points to serious problems with the ring, such as a broken cable. The beacon frame carries the address of the station thought to be down.
45. What are NetBIOS and NetBEUI?
- NetBIOS: Network Basic Input / Output System
An application-programming 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 lower-level 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, department-size local area networks (LANs) of 1 to 200 clients. It can use Token Ring source routing as its only method of routing.
46. What is the most common IP version presently in use?
The most common IP version now in use is version 4.
47. What is fragmentation? What fields of the IP header are used for fragmentation?
Routers perform fragmentation when a packet is longer than the maximum packet length (Maximum Transmission Unit, or MTU) supported by a data link onto which the packet must be transmitted. The data within the packet will be broken into fragments, and each fragment will be encapsulated in its own packet. The receiver uses the Identifier and Fragment Offset fields and the MF bit of the Flags field to reassemble the fragments.
48. What is the purpose of the TTL field in the IP header? How does the TTL process work?
The Time to Live (TTL) field prevents “lost” packets from being passed endlessly through the IP internetwork. The field contains an 8-bit integer that is set by the originator of the packet. Each router through which the packet passes will decrement the integer by one. If a router decrements the TTL to zero, it will discard the packet and send an ICMP “time exceeded” error message to the packet’s source address.
49. What are the different memories used in a CISCO router?
Three types of memories are used in a CISCO router:
- NVRAM stands for Non-volatile random access memory.
- It is used to store the startup configuration file.
- NVRAM retains the configuration file even if the router shut down.
- DRAM stands for dynamic random access memory.
- It stores the configuration file that is being executed.
- DRAM is used by the processor to access the data directly rather than accessing it from scratch.
- DRAM is located near the processor that provides faster access to the data than the storage media such as hard disk.
- Simple design, low cost, and high speed are the main features of DRAM memory.
- DRAM is a volatile memory.
- It is used to store the system IOS.
- Flash memory is used to store the ios images.
- Flash memory is erasable and reprogrammable ROM.
- The capacity of the flash memory is large enough to accommodate many different IOS versions.
50. 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.
51. What are the various modes in VTP?
There are three modes in VTP :
- Server mode
- Client mode
- Transparent mode
Default mode is server.
- Server mode- Full control over VLAN creations and modifications for their domains.
- Client mode- VTP clients do not allow the administrator to create, change or delete any VLAN; instead they listen to the VTP’s advertisements from other switches and modify their VLAN configuration accordingly.
- Transparent mode- VTP transparent mode switches will not participate in VTP advertisements. It can create and delete VLANs that are local only to itself. It will not propagate to other switches, and will not advertise its own VLAN configuration.
52. What is the Attenuation?
In communication weakening or loss of signal energy, typically caused by distance.
53. What is the MAC address?
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.
54. What is the ICMP protocol?
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.
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55. What is the difference between ARP and RARP?
- 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.
56. What is the first octet rule?
The first octet rule determines the class of an IP address as follows:
Class A: The first bit of the first octet is always 0.
Class B: The first two bits of the first octet are always 10.
Class C: The first three bits of the first octet are always 110.
Class D: The first four bits of the first octet are always 1110.
Class E: The first four bits of the first octet are always 1111.
57. How are class A, B, and C IP addresses recognized in dotted decimal? How are they recognized in binary?
The A, B, C IP addresses are recognized in dotted decimal and binary as follows:
Class Binary Range of First Octet Decimal Range of First Octet
A 0000000 – 01111110 1 – 126
B 10000000 – 10111111 128 – 191
C 11000000 – 11011111 192- 223
58. What is an address mask, and how does it work?
An IP address mask identifies the network part of an IP address. Each one in the 32-bit mask marks the corresponding bit in the IP address as a network bit. A zero in the mask marks the Corresponding bit in the IP address as a host bit. A Boolean AND is performed in all 32 bits of the address and the mask; in the result, all network bits of the mask will be repeated, and all host bits will be changed to zero.
59. What happens if there is no VLAN in switch ports?
If there is no VLAN in switches, it can lead to a broadcast storm; as all ports will start broadcasting. By default all ports in switches are in VLAN1 and they can send and receive data within VLAN1. We can also create multiple VLANs and join them using routers.
60. What is route poisoning?
Route poisoning is a technique of preventing a network from transmitting packets through a route that has become invalid.
61. What route entry will be assigned to dead or invalid routes in case of RIP?
In the case of RIP table entry, 16 hops will be assigned to dead or invalid routes making it unreachable.
62. Explain how an SPF algorithm works?
A router builds a shortest path tree by first adding itself as the root. Using the information in the topological database, the router creates a list of all of its directly connected neighbors. The lowest cost link to a neighbor becomes a branch of the tree, and that router’s neighbors are added to the list. The list is checked for duplicate paths, and if they exist, the higher-cost paths are removed from the list. The lowest-cost router on the list is added to the tree, that router’s neighbors are added to the list, and the list is again checked for duplicate paths. This process continues until no routers remain on the list.
63. How do areas benefit a link state inter network?
Within a routing domain, areas are subdomains. They make link state routing more efficient by limiting the size of the link state database of each router in the area.
64. What is an autonomous system?
Depending on the usage, an autonomous system can be defined as an inter network under a common administrative domain or a single routing domain.
65. 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.
66. 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 a growing large network, it’s better to start segmenting the network and create subnet masks for different segments.
67. Differentiate User Mode from Privileged Mode
User Mode is used for regular tasks 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.
68. 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 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.
69. What is BootP?
BootP is a protocol which is used to boot diskless workstations connected to the network. It is a short form for Boot Protocol. Diskless workstations use BootP in order to determine its own IP address as well as the IP address of the server PC.
70. What is the relation between Bit and Byte?
8 Bits make 1 Byte.
71. What is the use of Bit and Byte?
The bit is used to measure the speed (Bandwidth). A byte is used to measure storage capacity(Space).
72. 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.
73. How does cut-through LAN switching work?
In Cut-Through LAN switching, as soon as the router receives the data frame, it immediately sends it out again and forwards it to the next network segment after reading the destination address without checking FCS.
74. 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.
75. What is HDLC?
HDLC is a short form of High-Level Data Link Control protocol and is a proprietary protocol of CISCO. It is the default encapsulation operated within CISCO routers.
76. How are internetworks created?
Internet works are created when networks are connected using routers. Specifically, the network administrator assigns a logical address to every network that connects to the router
77. What is Bandwidth?
Bandwidth refers to the transmission capacity of a medium. It is a measure of how much volume a transmission channel can handle and is measured in Kbps.
78. How does Hold-downs work?
Hold-downs prevent regular update messages from reinstating a downed link by removing that link from update messages. It uses triggered updates to reset the hold-down timer.
79. What are the ranges for the private IP’s?
Ranges for private IPS are
- Class A: 10.0.0.0 – 10.0.0.255
- Class B: 172.16.0.0 – 172.31.0.0
- Class C: 192.168.0.0 – 192.168.0.255
80. In how many ways you can access the routers?
You can access routers in three ways
- Telnet (IP)
- AUX (Telephone)
- Console (Cable)
81. Explain what is EIGRP?
EIGRP stands for Enhanced Interior Gateway Routing Protocol; it is a routing protocol designed by Cisco Systems. It is availed on a router to share routes with other routers within the same autonomous system. Unlike other routers like RIP, EIGRP only sends incremental updates, decreasing the workload on the router and the amount of data which needs to be transferred.
82. Which are the two types of available cables?
At the present time, the following types of cables are available to use in networking:
- Crossover cable
- Straight through cable
83. What are the functions of CDP?
CDP is used for Cisco Discovery protocol that is a layer 2 protocol and works on the basis of MAC address. It is also used to find the adjacent Cisco devices. It can be used to find out port numbers, iOS details, IP addresses, switch models, router models, interface details and device ID.
84. Can you differentiate half duplex and full duplex?
In half-duplex, the communication will occur only in one direction while the communication will occur in both the directions in full duplex. It is one of the important CCNA interview questions that you should know during the preparation for the interview.
85. What do we check while configuring the server?
While configuring, the following parameters are checked:
- Check whether LAN is connected or not.
- The root should be in the NTFS format.
- The server should have a static IP address for communication.
86. What is the Domain Name System (DNS)?
DNS is an internet service that translates domain names into IP addresses. Anything connected to the internet i.e. mobile phones, laptops, websites etc. has an IP address that is uniquely defined
87. What is an administrative distance?
An administrative distance is a rating of preference for a routing protocol or a static route. Every routing protocol and every static route has an administrative distance associated with it. When a router learns of a destination via more than one routing protocol or static route, it will use the route with the lowest administrative distance.
88. What is a floating static route?
A floating static route is an alternative route to a destination. The administrative distance is set high enough that the floating static route is used only if a more-preferred route becomes unavailable.
89. What is the difference between equal-cost and unequal-cost load sharing?
Equal-cost load sharing distributes traffic equally among multiple paths with equal metrics.
Unequal-cost load sharing distributes packets among multiple paths with different metrics. The traffic will be distributed inversely proportional to the cost of the routes.
90. How does the switching mode at an interface affect load sharing?
If an interface is fast switched, per destination load sharing is performed. If an interface is process switched, per packet load sharing is performed.
91. What is a recursive table lookup?
A recursive routing table lookup occurs when a router cannot acquire all the information it needs to forward a packet with a single routing table lookup. For example, the router may perform one lookup to find the route to a destination and then perform another lookup to find a route to the next hop router of the first route.
92. What is the point-to-point protocol in CCNA?
The point-to-point protocol is an industry standard suite of protocols which uses the point-to-point link to transport multiprotocol datagram. The point-to-point protocol is a WAN protocol used at layer 2 to encapsulate the frames for the data transmission over the physical layer.
Following are the features that point-to-point protocol provides:
- Link quality management: It is a technique to monitor the quality of a link. If it finds any error in a link, then the link is shut down.
- The point-to-point protocol also provides authentication.
- It provides some essential features such as authentication, error detection, link quality monitoring, load balancing, compression, etc.
Components of a point-to-point protocol are:
- Encapsulation: Point-to-point protocol encapsulates the network packets in its frames using HDLC protocol. This makes the PPP layer three layer independent.
- Link Control Protocol: Link Control Protocol is used for establishing, configuring and testing the data link over internet connections.
- Network Control Protocol: Point-to-point protocol is used in a data link layer in the OSI reference model. The data comes from the upper layer, i.e., transport layer or network layer is fully compatible with PPP due to the presence of a Network control protocol.
93. What metric does RIP use? How is the metric used to indicate an unreachable network?
RIP uses a hop count metric. An unreachable network is indicated by setting the hop count to 16, which RIP interprets as an infinite distance.
94. What is the update period for RIP?
RIP sends periodic updates every 30 seconds minus a small random variable to prevent the updates of neighboring routers from becoming synchronized.