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Prime 50 CCNA Interview Questions and Solutions

CCNA is a certification that proves your skill to know, use, and handle Cisco networks. The CCNA certification gives you with the talents crucial for optimizing and administering Cisco networking assets in a company. With this credential, you may transfer on to higher-level certifications such because the MCSA or MCDBA. 

The advantages of acquiring CCNA embody:

  • Improved job prospects: A well-rounded CCNA certification signifies that you’ve got data about community applied sciences and their functions – two vital components when searching for employment in data know-how (IT) fields.  
  • Elevated data base: Understanding administer Cisco networks permits IT, professionals, extra flexibility when deploying techniques inside a company, they now not want somebody who solely understands {hardware} configurations.

On this article, we are going to see the highest 50 CCNA interview questions with their solutions. 


1. Identify any two ports of Switches. 

  • Entry Port: An entry port is a sort of connection on a swap that can be utilized to attach a digital machine on VLAN unaware. This port delivers the digital machine with connectivity by a swap that’s VLAN conscious with out requiring it to assist VLAN tagging.
  • Combo Port: These ports are used to attach units to the swap. Switches are linked to a port that known as a combo port. These ports will be assigned to completely different mixtures of units. A tool mixture is a gaggle of a number of units used to transmit or obtain knowledge. In different phrases, a combo port could be a single interface with two entrance ends, corresponding to an RJ45 connector and an SFP module connector (additionally known as MiniGBIC).

2. What are three doable methods of knowledge transmission in CCNA?

  • Simplex Mode: Simplex mode is type of a unidirectional path inside the communication is one-way. Just one of the two units will ship and the opposite will obtain. 
  • Half-Duplex Mode: Each station will broadcast and obtain data in half-duplex mode, nevertheless, it’s not on the an identical time. as soon as the gadget transmits knowledge.
  • Full-Duplex Mode:  Every station will broadcast and obtain data at an an identical time in full-duplex mode. Alerts touring in a single path share the hyperlink’s functionality with alerts touring inside the completely different instructions in full-duplex mode:
    • Both the connection or the receiver will need to have two bodily unbiased transmission routes.
    • Then again, capacitance is split by alerts transferring in each instructions.

For extra particulars please seek advice from the Transmission Modes in Pc Networks (Simplex, Half-Duplex, and Full-Duplex) article.

3. Identify completely different IPX entry lists.

There are three IPX Entry lists:

  • Normal Entry checklist: The entry checklist is created utilizing the supply IP tackle. These ACLs enable or deny the entire protocol suite. They don’t differentiate between the IP site visitors corresponding to TCP, UDP, HTTPS, and so forth. Through the use of digits 1-99 or 1300-1999, the router will perceive it as a normal ACL and set the tackle because the supply IP tackle.
  • Prolonged Entry-list: It’s a sort of Entry-list that’s primarily used as it could actually differentiate IP site visitors. the entire site visitors won’t be permitted or denied like in the usual entry checklist. ACL makes use of each supply and vacation spot IP addresses and likewise port numbers to differentiate IP site visitors. In one of these ACL, we will additionally point out which IP site visitors needs to be allowed or denied. These use vary of numbers 100-199 and 2000-2699.
  • Reflexive Entry checklist: Reflexive Entry-list will be outlined as an entry checklist that enables solely the responses of the packets on periods created inside the community from the surface community.

For extra particulars please seek advice from the Entry-Lists (ACL) article.

4. What do you imply by 100BaseFX?

100BASE-FX is one other variation of the 100Base-T regular with the exception that it’s a fast LAN i.e sending over fiber. Like numerous requirements, 100Base makes use of two wires or on this case strings for knowledge transmission: one for reception (RX), whereas the opposite for transmission (TX).

For extra particulars please seek advice from the Quick Ethernet and Gigabit Ethernet article.

5. Identify the LAN Switching methodology that’s principally utilized in CISCO Catalyst 5000?

The shop-and-forward switching method is utilized by the CISCO Catalyst 5000 and due to this fact it shops the whole body in its buffers and performs a CRC (Cyclic Redundancy Test)  earlier than deciding whether or not or to not transmit this data body.

For extra particulars please seek advice from the Message switching methods article.

6. Identify completely different recollections which might be utilized in CISCO routers.

The completely different recollections which might be utilized in Cisco routers are given beneath:

  • Flash Reminiscence 
  • RAM ( Random Entry Reminiscence ) 
  • ROM (Learn Solely Reminiscence)
  • NVRAM (Non-Unstable Random Entry Reminiscence)

For extra particulars please seek advice from the completely different recollections utilized in a CISCO router article.

7. What’s the distinction between tracert and traceroute?

Traceroute is a characteristic or a utility that information the route (express passage PCs at every bounce) by means of the group between your PC and a predetermined goal PC and the Tracert monitoring is a fast scan that reveals loads of monitoring data of any community or gadget that may be obtained in a package deal from a PC or gadget.

For extra particulars please seek advice from the Distinction between Ping and Traceroute article

8. What do you imply by DLCI?

DLCI (Knowledge Hyperlink Connection Identifier) is the amount of a private or switched digital circuit in a body relay community, located inside the body header, the DLCI discipline identifies that logical circuit the info travels over, and every DLCI features a dedicated data charge (CIR) related to it.

For extra particulars please seek advice from the Native Administration Interface (LMI)

9 . Identify router command that’s used to show RAM content material and NVRAM Content material.

To Present, the parts of NVRAM or level to the association file assigned to the CONFIG_FILE variable, we use the present startup-config command.

For extra particulars please seek advice from the Cisco Router fundamental instructions article.

10. Outline Body relay?

Body relay is a know-how that gives quick and dependable knowledge transmission in Web networks. It’s a standards-based networking know-how that gives a path for knowledge packets from one level on the community to a different.

For extra particulars please seek advice from the How does Body Relay Work article.

11. Distinction between Consumer mode and Privileged mode in Cisco? 

Consumer mode is just for viewing router configurations and Privileged mode is for viewing all router configurations and likewise permits modifying some much less vital configurations.

For extra particulars please seek advice from the Cisco Router modes article.

12. What’s EIGRP? Point out some metrics of the EIGRP Protocol.

EIGRP determines the trail worth from 5 metrics: bandwidth, load, delay, reliability, and MTU. EIGRP makes use of 5 completely different messages to speak with neighboring routers. EIGRP Messages – Hi there, Replace, Query, Reply and Affirm.

For extra particulars please seek advice from the EIGRP fundamentals article.

13 . What’s CDP(Cisco Discovery Protocol)? Write its capabilities.

Cisco Discovery Protocol (CDP) is a community discovery device that helps community directors and technicians determine close by Cisco units, particularly these with a low-transparency protocol.

For extra particulars please seek advice from the Cisco Discovery Protocol (CDP) and Hyperlink Layer Discovery Protocol (LLDP) article.

14. Distinction between a broadcast area and a collision area?

Each broadcast and collision domains overlap. Broadcast area refers back to the transmission of data over a large space, corresponding to tv or radio broadcasting. The collision area consists of two or extra objects that come into contact with one another abruptly, violently, or unexpectedly.

For extra particulars please seek advice from the Collision Area and Broadcast Area within the Pc Community article.

15. What do you imply by route poisoning?

Route poisoning is a approach to management a router from transmitting packets by means of a path that has develop into weak inside laptop networks. Distance-vector routing protocols in laptop networks use route poisoning to point out different routers {that a} route is now not reachable and shouldn’t be thought-about from their routing tables. The cut up horizon with poison reverses the route poisoning and delivers updates with unreachable hop counts on to all of the nodes within the community. When the protocol catches an invalid route, all the routers within the community are notified that the dangerous route has an infinite (∞) route metric. This makes all nodes on the invalid route appear infinitely distant, stopping any of the routers from sending packets over the invalid path.

For extra particulars please seek advice from the Route Poisoning article.

16. What sorts of passwords can be utilized in CISCO routers?

There are three sorts of passwords that can be utilized in a Cisco router. These are 

  • Administrative passwords: They’re used to manage entry to the router. They’re used to assign permissions to customers and to manage the general operation of the router. 
  • Consumer passwords: These are used to guard knowledge saved on the router. They’re used to log into the router and management entry to the router.
  • Password attributes: They’re used to set a password restrict, and to specify the period of time {that a} password should be used earlier than it’s robotically modified.

For extra particulars please seek advice from the Totally different Kinds of Passwords utilized in Securing Cisco Router article.

17. Write the distinction between public IP and personal IP.

A public IP tackle that identifies you on the Web so that every one the data you search can discover you. Non-public IP addresses are used inside a non-public community to securely connect with different units in the identical community. Every gadget on the identical community has a singular non-public IP tackle.

For extra particulars please seek advice from the Non-public and Public IP article.

18. Clarify PoE.

Energy over Ethernet (PoE) is a measure that enables Ethernet cables to concurrently switch knowledge and energy utilizing a single community cable. This allows system integration and community installers to determine powered home equipment in areas that lack electrical circuitry. As well as, PoE stops the price of putting in further electrical wiring, requiring skilled electrical installers to guarantee that strict conduit laws are adopted. PoE know-how transmits 10/100/1000 Mbps of knowledge and 15W, 30W, 60W, and as much as 90W of energy finances to home equipment over Cat5e, Cat6, and Cat6a. Cat7 and Cat8 Ethernet cables for the very best distance of 100m.

For extra particulars please seek advice from the Energy Over Ethernet (POE) article.

19. What’s Spherical Journey Time?

RTT is also called round-trip time is an important device in defining the working situation of a community. It’s the time between a request and the response in any sort of server on the web. A round-trip time is measured in milliseconds. RTT will be examined and decided by pinging a selected tackle. It refers back to the time taken by a community request to succeed in a closing level and to revert again to the preliminary supply.

For extra particulars please seek advice from the RTT(Spherical Journey Time) article.

20. What’s DHCP scope?

The DHCP scope is a legitimate vary of IP addresses which might be identified for project or lease to consumer computer systems on a person subnet. In a DHCP server, a scope is configured to find out the tackle pool of IPs that the server can present to DHCP purchasers. DHCP Scopes outline IP addresses which might be offered to the purchasers. They need to be decided and activated earlier than DHCP purchasers use the DHCP server for its dynamic IP configuration. Customers can configure as many scopes on a DHCP server as wanted within the community atmosphere.

For extra particulars please seek advice from the Dynamic Host Configuration Protocol (DHCP) article.

21.  what’s NVRAM?

NVRAM (Non-volatile random-access reminiscence) is a pc reminiscence that may preserve knowledge when energy to the reminiscence chips has been turned off. NVRAM is part of the bigger sort of non-volatile reminiscence (NVM), which accommodates storage-class reminiscence primarily based on NAND flash. Flash reminiscence chips are gradual to learn to and write than RAM chips, making them much less properly fitted for lively computational reminiscence.

22. What’s using “Service Password Encryption”?

Service Password Encryption  Command on CISCO Router/Swap  Allows you to encrypt all passwords in your router in order that they can’t be simply assumed out of your operating configuration. This command makes use of very weak encryption as a result of the router has to decrypt the password in a short time for it to work.

For extra particulars please seek advice from the Totally different Kinds of Passwords utilized in Securing Cisco Router article.

23.  Clarify completely different cable sorts?

There are generally two sorts of cables utilized in networking, described beneath.

  • Coaxial cable: A coaxial cable is a sort of copper cable specifically made with a steel guard and different elements organized to cease sign interference. It’s primarily utilized by cable TV corporations to attach their satellite tv for pc antenna installations to prospects’ properties and companies. It’s also generally utilized by phone firms to safe central workplaces to phone poles close to prospects. Some properties and workplaces use coaxial cable, too, however its common use as an Ethernet connectivity medium in firms and knowledge facilities has been changed by the deployment of twisted pair cabling.
  • Twisted pair: Twisted pair Ethernet is an Ethernet in a pc community that makes use of twisted pairs of insulated copper wires for the bodily layer of the community, which is linked to the info hyperlink layer. Twisted pair cable wires are circled one another to scale back obstacles from different twisted pairs within the cable. The 2 twisted wires assist in decreasing crosstalk that may disrupt alerts and reduce electromagnetic induction, which has a voltage throughout a conductor transferring by means of a magnetic discipline. 

For extra particulars please seek advice from the Kinds of Ethernet Cable article.

24.  What’s the port variety of DNS and Telnet?

The Port variety of Telnet is 23 and the Port variety of DNS is 53..

For extra particulars please seek advice from the Numerous TCP and UDP ports article.

25. Which service makes use of each TCP and UDP?

The Area Identify System (DNS) makes use of the TCP and UDP protocols for communication.UDP is used for decrease communications and is right for DNS queries.TCP is used for zone transfers and is appropriate for giant response messages.

For extra particulars please seek advice from the Numerous TCP and UDP ports article.

26. What’s the port variety of SMTP and POP3?

The Port variety of SMTP is 587 and the Port variety of POP3 is 110.

For extra particulars please seek advice from the Distinction between SMTP and POP3 article.

27. What’s CRC? Which layer does CRC work on?

CRC stands for Cyclic Redundancy Test. It’s a checksum algorithm used to detect errors in digital knowledge streams transmitted between two or extra computer systems. The layer the place CRC works will depend on the kind of knowledge being checked and the way it must be processed by the system. Usually, CRC is utilized on the decrease layer of an OSI mannequin stack (OSI Reference Mannequin).

For extra particulars please seek advice from the Cyclic Redundancy Test article.

28. Which one is dependable – TCP or UDP ? and why?

TCP is dependable as a result of it ensures the supply of knowledge to the vacation spot router. The supply of knowledge to the vacation spot cannot be secured in UDP.

For extra particulars please seek advice from the Numerous TCP and UDP ports article.

29. What’s the port variety of FTP (knowledge) and FTP?

The Port variety of FTP (knowledge) is 20 and the Port variety of FTP is 21. 

For extra particulars please seek advice from the File Switch Protocol (FTP) article.

30.  Which layer gives the logical addressing that routers will use for path dedication?

The Community layer gives logical addressing, usually IP addressing and routing.

For extra particulars please seek advice from the Community Layer Companies- Packetizing, Routing, and Forwarding article.

31. DNS makes use of which protocol? Why?

The Area Identify System (DNS) makes use of Transmission Management Protocol (TCP) for zone transfers and Consumer Datagram Protocol (UDP) for title queries.UDP exchanges fewer knowledge than TCP.

For extra particulars please seek advice from the  Why does DNS use UDP and never TCP article.

32. Differentiate between forwarding lookup and reverse lookup in DNS?

Ahead DNS and reverse DNS lookups are two completely different strategies of accessing the Web. The ahead space is the DNS zone the place the hostname is saved within the IP tackle relationship. Reverse DNS is the question methodology for figuring out the area title related to an IP tackle.

For extra particulars please seek advice from the Learn how to Implement Reverse DNS Look Up Cache? article.

33. What’s Break up Horizon Cisco?

A cut up horizon is developed to cease routing loops. Routing loops occur when a loop is created between two or extra routers. For instance, Router 1 has a community path to by way of Router 2. Router 2 has a path to the identical community, however it’s again by way of Router 1. Subsequently, Router 1 sends packets for to Router 2, which then transmits the packets again to Router 1. This looping continues till the TTL (Time to Dwell) on the packet expires.

For extra particulars please seek advice from the  Route Poisoning and Rely to infinity downside within the Routing article.

34. Why is RIP often called Distance Vector?

The Routing Info Protocol (RIP) is the oldest distance-vector routing protocol that makes use of the hop depend as a routing metric. RIP stops routing loops by executing a restrict on the variety of hops approved in a path from supply to vacation spot. The biggest variety of hops allowed for RIP is 15, which limits the dimensions of networks that RIP can assist. RIP executes the cut up horizon, route poisoning, and hold-down means to forestall the flawed routing data from being propagated. In RIPv1 routers broadcast updates with their routing desk each 30 seconds. Within the early deployments, routing tables had been brief sufficient that the site visitors was not vital. As networks grew in dimension, nevertheless, it grew to become apparent there may very well be an enormous site visitors burst each 30 seconds, even when the routers had been initialized at random occasions. 

For extra particulars please seek advice from the Routing Info Protocol (RIP) article.

35. What’s the administrative distance of RIP?

By default, OSPF has a default administration degree of 110 and RIP has a default administration degree of 120.

For extra particulars please seek advice from the Routing Info Protocol (RIP) article.

36. What’s the restrict of hop depend in RIP?

The restrict of hop depend in RIP is 15. Networks with a hop depend of 16 or extra are unreachable.

For extra particulars please seek advice from the Routing Info Protocol (RIP) article.

37. How is RIP choose the perfect path to the distant community?

The primary perform of the router is to find out one of the simplest ways to ship the packets. To find out the perfect route, a router searches its router desk to discover a community tackle just like the vacation spot IP tackle of the package deal.

For extra particulars please seek advice from the Routing Info Protocol (RIP) article.

38. What are the variations between RIPv1 and RIPv2?

RIPv1 makes use of a normal route. Occasional updates should not have subnet data and no assist for VLSM. This limitation makes it not possible to have subnets of various sizes inside the similar community class. In different phrases, all subnets within the community class needs to be the identical dimension. There’s additionally no router authentication assist, which makes RIP susceptible to numerous assaults. RIPv2 is a vector distance route protocol outlined in RFC 1723. As a phaseless protocol, it means, it included a subnet masks and community addresses in its router updates.

For extra particulars please seek advice from the Variations between RIPv1 and RIPv2 article.

39. What’s pinhole congestion?

In laptop networking, the router makes choices relating to the best way a packet will journey, primarily based on the variety of hops it carries to succeed in the vacation spot and if it had 2 different methods to get there, it can solely ship it by way of the shortest path, whatever the connection pace. This is called pinhole congestion.

For extra particulars please seek advice from the Congestion Management in Pc Networks article.

40. What’s a passive interface in RIP?

Router (config-router) # passive-interface serial0 / 0/0. Units the interface as idle, which means that route updates won’t be despatched to this interface. NOTE: In RIP, the passive-interface command will forestall the inter-face from sending route updates however will enable the visible interface to obtain updates.

For extra particulars please seek advice from the Passive-Interface Command Habits in RIP, EIGRP & OSPF article.

41. Clarify the loop avoidance mechanism in RIP.

The next strategies are used to keep away from Routing Loops in RIP:

  • The utmost hop depend mechanism can be utilized to dam Routing Loops. Vector distance protocols use the TTL (Lifetime) worth within the IP knowledge header to keep away from loops.
  • Break up horizontal is the setting of the route that stops the route from being marketed again to the place it got here from.
  • Route Poisoning is one other approach to keep away from loops. If the router finds that one among its linked routes has failed, the router will likely be poisonous to the route by offering infinite metrics to it.

For extra particulars please seek advice from the  Routing Loop and Learn how to Keep away from Routing Loop article.

42. Why EIGRP known as hybrid protocol?

EIGRP doesn’t switch all knowledge to the Routing desk when modifications are made, however will solely switch modifications made for the reason that Routing desk was final up to date. EIGRP doesn’t ship its routing desk periodically, however will solely ship routing knowledge within the occasion of an actual change. This habits is extremely compliant with link-state routing laws, so EIGRP is taken into account a hybrid protocol.

For extra particulars please seek advice from the EIGRP fundamentals article.

43.  What is supposed by lively and passive states in EIGRP?

  • Lively State: Routes the place a follower route fails and no follower routes are more likely to transfer to a purposeful state forcing EIGRP to submit question packages and reconnect. 
  • Passive State: The route is in a passive state the place the route has a path to comply with, and no failures have occurred up to now.

For extra particulars please seek advice from the EIGRP fundamentals article.

44. What does stuck-in-active imply?

EIGRP is a dependable protocol and for every query the route you ship to its neighbors it’s essential to get a response inside 3 minutes. If the router doesn’t get a solution to ALL its pending questions it can set the stage for SIA (STUCK INACTIVE) and kill the closest neighbor.

45.  What’s the EIGRP Feasibility Situation?

The Feasibility situation states that the route won’t be accepted if the Reported Vary exceeds the very best Route vary. Or it means one other means from a router’s perspective: the trail to the community won’t be accepted if my neighbor’s price exceeds my price. 

For extra particulars please seek advice from the EIGRP Price Calculation article.

46. Clarify what is going to occur if the packet isn’t acknowledged?

If a packet isn’t acknowledged by the community, it signifies that the info was efficiently delivered to its vacation spot however no response was acquired from both finish. So long as each ends are conscious of one another and have been configured accurately, there needs to be no cause for the receiving node to do something additional with this packet. Knowledge should still be flowing by means of this connection as a result of acknowledgments take the time or as a result of some intermediate nodes could be buffering packets earlier than forwarding them on. Nevertheless, if at any time limit you discover your site visitors slowing down noticeably or changing into utterly unavailable resulting from an extreme variety of misplaced packets (particularly throughout high-traffic occasions), then it’s probably that one thing has gone flawed and also you’ll want to analyze what triggered it.

For extra particulars please seek advice from the Cease and Look ahead to protocol, and its issues, and options article.

47. Clarify Null Zero in EIGRP?

It’s a visible interface used to make sure that routes enter the RIB, the tracks will need to have the next-hop to get into the RIB. If a packet arrives on a tool with a path to Null 0 and isn’t elsewhere, it can get rid of it because the ACL would. Consider it as a visual interplay when the packets die properly.

For extra particulars please seek advice from the article EIGRP fundamentals 

48.  What’s the EIGRP stub routing characteristic?

The EIGRP stub routing characteristic permits the community administrator to forestall queries from being despatched to a distant gadget. Along with a easy hub and spoke community, the place the distant gadget is linked to a single distribution gadget, the distant gadget can have a twin house on two or extra distribution units.

49. Distinction between LSA & LSU in OSPF?

Hyperlink State Replace (LSU) packs are OSPF Kind 4. packs. Every LSA accommodates route, metrics, and topology data to outline a part of the OSPF community. The native router advertises the LSA contained in the LSU package deal to its neighbors.

50.  What’s Route Redistribution in laptop networks?

Using a routing protocol to broadcast routes which might be identified by another means, corresponding to by one other routing protocol, static routes, or instantly linked routes, known as redistribution. Whereas working a single routing protocol all through your complete IP internetwork is fascinating, multi-protocol routing is frequent for plenty of causes, corresponding to enterprise unions, a number of departments managed by a number of community directors, and multi-vendor environments. Operating different routing protocols is often a part of a community design. In any case, having a a number of protocol atmosphere makes redistribution a necessity.



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