Most Important 345 CCNA Interview Questions [UPDATED 2020]

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If you are a Networking aspirant and looking to kick start your high flying career in Networking Domain then, here is a list of TOP CCNA interview questions. These questions will help you clear you in qualifying your technical interviews.

The interview questions have been divided into 9 Categories for Answers of these Questions click on individual links.

Updated: We are working on aswers other categoroes will be updated soon

  1. Basic Interview Questions 
  2. OSI Model Interview Questions
  3. RIP Interview Questions
  4. EIGRP Interview Questions
  5. OSPF Interview Questions
  6. STP Interview Questions
  7. VLAN Interview Questions
  8. VTP Interview Questions
  9. Wireless Interview Questions

Recommedned Read:

  • What is CCNA, CCNP and CCIE
  • Scope and Importance of CCIE

Basic Networking Interview Questions

  1. Define Network?
  2. What is a Link?
  3. What is a node?
  4. What is a gateway?
  5. What is point-point link?
  6. What is Multiple Access?
  7. What’s the benefit of subnetting?
  8. What is BGP (Border Gateway Protocol)?
  9. What is Gateway-to-Gateway protocol?
  10. What is a Multi-homed Host?
  11. What is OSPF?
  12. What is Routing?
  13. What is a Protocol?
  14. Explain difference between Router,Switch and Hub ?
  15. What is Checksum?
  16. What is Redundancy ?
  17. What are the criteria necessary for an effective and efficient network?
  18. What is the key advantage of using switches?
  19. When does network congestion occur?
  20. Does a bridge divide a network into smaller segments?
  21. What is the difference between OSI and TCP/IP Model ?
  22. What is the size of IP Address?
  23. What is the range of class C address?
  24. What is PoE (Power over Ethernet) ?
  25. What are the advantages of Distributed Processing?
  26. When were OSI model developed and why its standard called 802.XX and so on?
  27. What is Full form of AD?
  28. What is a peer-peer process?
  29. What is the difference between broadcast domain and collision domain ?
  30. What is ping? Why you use ping?
  31. Explain difference between straight and crossover cable with examples ?
  32. What is the difference between tracert and traceroute
  33. What is Round Trip Time?
  34. Define the terms Unicasting, Multiccasting and Broadcasting and Anycasting?
  35. How many pins do serial ports of routers have?
  36. What are the differences between static ip addressing and dynamic ip addressing?
  37. Difference between CSMA/CD and CSMA/CA ?
  38. What is DHCP scope?
  39. What are the different memories used in a CISCO router?
  40. What are the different types of passwords used in securing a CISCO router?
  41. What is the use of “Service Password Encryption” ?
  42. Brielfly explain the conversion steps in data encapsulation.?
  43. In configuring a router, what command must be used if you want to delete the configuration data that is stored in the NVRAM?
  44. IEEE standard for wireless networking?
  45. What is the range of class A address?
  46. What is the range of class B address?
  47. Differentiate Logical Topology from Physical Topology?
  48. what is AS (Autonomous System) ?
  49. What is the difference between Private IP and Public IP ?
  50. Explain different cable types ?
  51. How does RIP differ from EIGRP?
  52. Differentiate User Mode from Privileged Mode
  53. What is 100BaseFX?
  54. Differentiate full-duplex from half-duplex ?
  55. What does the show protocol display?

OSI Model Interview Questions

  1. List the layers of OSI ?
  2. What are the responsibilities of Data Link Layer?
  3. What are the responsibilities of Network Layer?
  4. What are the responsibilities of Transport Layer?
  5. Routers work at which OSI layer?
  6. Switches work at which OSI layer?
  7. What is a Window in networking terms?
  8. What is the role of the LLC sublayer in datalink layer?
  9. What is the function of the Application Layer in networking?
  10. What are the difference between TCP and UDP?
  11. What is the port no of DNS and Telnet?
  12. Which service use both TCP and UDP ?
  13. What is the port no of SMTP and POP3?
  14. In which layer term “Frames” is used ?
  15. In which layer term “Packets” is used ?
  16. In which layer term “Segments” is used ?
  17. Give some example for protocols work at Application layer ?
  18. What is CRC? Which layer CRC works ?
  19. What is the purpose of the Data Link?
  20. Which one is reliable – TCP or UDP ?
  21. What is the port number of ftp (data) and ftp?
  22. Which layer provides logical addressing that routers will use for path determination ?
  23. Which layer specifies voltage, wire speed, and pinout cables and moves bits between devices ?
  24. Which layer combines bits into bytes and bytes into frames, uses MAC addressing, and provide error detection ?
  25. Which layer is responsible for keeping the data from different applications separate on the network ?
  26. Which layer segments and resembles data into a data stream ?
  27. Which layer provides the physical transmission sof the data and handless error notification, network topology, and flow control ?
  28. Which Layer manages device addressing, tracks the location of devices on the network, and determine the best way to move data ?
  29. How Data breaks down on each layer from top to bottom ?
  30. MAC address works on which layer ? What are the differences of MAC sublayer and LLC sublayer?
  31. Which layer is responsible for converting data packets from the Data Link layer into electrical signals ?
  32. At which layer is routing implemented, enabling connections and path selection between two end systems. ?
  33. Which layer defines how data is formatted, presented, encoded,and converted for use on the network ?
  34. Which layer is responsible for creating, managing and terminating sessions between applications ?
  35. DNS uses which protocol? Why?
  36. Which layer is closer to the user?
  37. Differentiate between forward lookup and reverse lookup in DNS?
  38. What is IPSec?
  39. What is the way to establish a TCP connection?
  40. What is the difference between flow control and error control?

RIP Interview Questions

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  1. What is Route Poisoning?
  2. What is Split Horizon ?
  3. Utilizing RIP, what is the limit when it comes to number of hops?
  4. Mulitcast address of RIP v2 ?
  5. Administristative distance of RIP ?
  6. Can we use RIP in a scenario having more than 15 routers ?
  7. What is the difference between RIP and RIPng?
  8. What is the multicast address that Rip v2 uses?
  9. What are the four timers in RIP?
  10. What is the difference between RIPV1 & RIPV2?
  11. Explain Load-Balancing in RIP?
  12. Explain Split Horizon?
  13. What is route poisoning?
  14. How do you stop RIP updates from propagating out an interface on a router?
  15. What is the administrative distance of RIP?
  16. How do we configure RIP? Specify the commands.
  17. If a Rip v2 router advertise it’s route, would it be received by all the devices on the network?
  18. Which transport layer protocol does RIP use and the associated port number?
  19. If a static route and a Rip learnt route is available on a router which entry would be chosen by the router to forward the packet?
  20. What is the major benefit of dynamic routing protocol like RIP over Static route?
  21. Can a subnet mask information be stored in a Rip v1 packet?
  22. Is a subnet mask field available in a Rip v2 packet?
EIGRP Interview Questions
  1. What is EIGRP?
  2. What are the different tables in EIGRP?
  3. Why EIGRP is called hybrid protocol?
  4. What are the different packets in EIGRP?
  5. Conditions for EIGRP neigbours.
  6. What is meant by active and passive states in EIGRP ?
  7. What are the different K-values used in EIGRP ?
  8. Does EIGRP require an ip default-network command to propagate a default route?
  9. Should I always use the eigrp log-neighbor-changes command when I configure EIGRP?
  10. Does EIGRP support secondary addresses?
  11. What debugging capabilities does EIGRP have?
  12. What are the advantages of EIGRP other routing protocol ?
  13. What is Advertised distance ?
  14. What is successor ?
  15. What is the muticast address used by EIGRP to send Hello packets ?
  16. What is “Stuck in Active” ?
  17. What types of Authentication is supported by EIGRP ?
  18. What is the use of “variance” Command in EIGRP?
  19. Internal and external Administrative distance in EIGRP ?
  20. What is Feasible successor ?
  21. What is “Graceful shutdown” ?
  22. Maximum path load balanced by EIGRP ?
  23. How EIGRP support unequal load balancing ?
  24. What happen when we enable passive interface in EIGRP ?
  25. What does the word serno mean on the end of an EIGRP topology entry when you issue the show ip eigrp topology command?

For example: show ip eigrp topology P, 2 successors, FD is 46163456 via (46163456/45651456), Serial0.2, serno 7539273 via (46163456/45651456), Serial2.6, serno 7539266

  1. What percent of bandwidth and processor resources does EIGRP use?
  2. Does EIGRP support aggregation and variable length subnet masks?
  3. Can I configure more than one EIGRP autonomous system on the same router?
  4. If there are two EIGRP processes that run and two equal paths are learned, one by each EIGRP process, do both routes get installed?
  5. When I configure EIGRP, how can I configure a network statement with a mask?
  6. What is “Goodbye” message recieved in EIGRP ?
  7. Who does load-balancing when there are multiple links to a destination?
  8. How can I use only one path when a router has two equal cost paths?
  9. What is the difference in metric calculation between EIGRP and IGRP?
  10. What is the EIGRP Stub Routing feature?
  11. How can I send a default route to the Stub router from the hub?
  12. What are different route types in EIGRP?
  13. What is an offset-list, and how is it useful?
  14. What does the neighbor statement in the EIGRP configuration section do?
  15. Why does the EIGRP passive-interface command remove all neighbors for an interface?
  16. Why are routes received from one neighbor on a point-to-multipoint interface that runs EIGRP not propagated to another neighbor on the same point-to-multipoint interface?
  17. What are the primary functions of the PDM?
  18. What are the various load-balancing options available in EIGRP?
  19. What does the %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor (Tunnel0) is down: holding time expired error message mean?
  20. From the 16:29:14.262 Poison squashed: 10.X.X.X/24 reverse message, what does poison squashed mean?
OSPF Interview Questions
  1. Why are loopbacks advertised as /32 host routes in OSPF?
  2. Which command in OSPF shows the network LSA information?
  3. What command would you use to create a totally stubby area?
  4. What the Hello packet carries when we enable OSPF ?
  5. What are LSA types?
  6. What are area types? Why there are different area concepts?
  7. What is the main importance of STUB network? Why it is been developed in OSPF?
  8. What will happen if we redistribute between different process ?
  9. What are the adjacency type ? Is adjacency is formed in between all the OSPF enabled routers or not ? Explain
  10. What are EXSTART and EXCHANGE state?
  11. If router ID are same between OSPF enabled routers will they form adjacency or not?
  12. What is LSA 7 and how it can be used?
  13. How we can connect a normal area to a backbone area if they are not directly connected.
  14. What is LSA in case of OSPF? It resemblance to which properties of EIGRP?
  15. What is OSPF’s metric? How is it identified in routing table? Does it support redistribution?
  16. What are the states used in OSPF when forming neighborship?
  17. What are the packet types does OSPF use? Explain Hello, Dead Timers, LSA, LSU, LSR packets.
  18. What will be Hello/Dead timers in network having link capacity of >T1 and <=T1?
  19. What is OSPF Router ID and how is it elected?
  20. What is the DR/BDR in OSPF? How these are elected and in what scenario?
  21. What are the multicast IPs used by OSPF? What multicast IP does DR/BDR router and non-DR use?
  22. How do I change the reference bandwidth in OSPF?
  23. How to generate default route in OSPF?
  24. How external routes are advertised generally (E1 or E2)? How to change from E2 to E1?
  25. What are the LSA’s available in STUB and totally stub network?
  26. What is OSPF super BackBone area?
  27. What is the concept of auto-cost in OSPF?
  28. IS there any DR and BDR concept in /31 network?
  29. What are the different network types in OSPF?
  30. How does OSPF calculate its metric or cost?
  31. What algorithm is used by OSPF if equal cost routes exist?
  32. Are OSPF routing protocol exchanges authenticated?
  33. What is the link-state retransmit interval, and what is the command to set it?
  34. What is the purpose of the variable IP-OSPF-Transmit-Delay?
  35. Can an OSPF default be originated into the system based on external information on a router that does not itself have a default?
  36. Can I use the distribute-list in/out command with OSPF to filter routes?
  37. How can I give preference to OSPF interarea routes over intra-area routes?
  38. Do I need to manually set up adjacencies for routers on the Switched Multimegabit Data Service (SMDS) cloud with the OSPF neighbor subcommand?
  39. When routes are redistributed between OSPF processes, are all shortest path first algorithm (SPF) metrics preserved, or is the default metric value used?
  40. How does Cisco accommodate OSPF routing on partial-mesh Frame Relay networks?
  41. Which address-wild-mask pair should I use for assigning an unnumbered interface to an area?
  42. Can I have one numbered side and leave the other side unnumbered in OSPF?
  43. Why do I receive the “cannot allocate router id” error message when I configure Router OSPF One?
  44. Why do I receive the “unknown routing protocol” error message when I configure Router OSPF One?
  45. Is it true that only the static option of the virtual link in OSPF allows discontiguous networks, regardless of the mask propagation properties?
  46. Are the multicast IP addresses mapped to MAC-level multicast addresses?
  47. Does the Cisco OSPF implementation support IP TOS-based routing?
  48. Does the offset-list subcommand work for OSPF?
  49. Do I need any special commands to run OSPF over BRI/PRI links?
  50. Which Cisco IOS Software release began support for per-interface authentication type in OSPF?
  51. How can you detect the topological changes rapidly?
  52. How does OSPF use two Multilink paths to transfer packets?
  53. Can we have OSPF run over a GRE tunnel?
  54. Is there a way to manipulate and prefer the Type 3 LSAs to originate from two different areas sent to the non-backbone area?
  55. What is the maximum number of OSPF processes (VRF aware) on 7600/6500 platforms?
  56. Is there a way to compare Cisco NX-OS/IOS OSPF commands?
  57. Is there any feature of OSPF protocol for quick convergence and a slow re-convergence of routes?

STP Interview Questions

  1. What is Spanning tree aka STP ?
  2. How does STP maintain a loop-free network?
  3. What parameters can be tuned to influence the selection of a port as a Root or Designated Port?
  4. What is BDPU ?what is the basics function of BPDU?
  5. What is the STP listening state?
  6. Which command enables RSTP on a switch?
  7. what is Per-VLAN Spanning Tree Protocol (PVST)
  8. What is the default bridge priority in a Bridge ID for all Cisco switches?
  9. Which STP version run default on cisco switches ?
  10. What is the purpose of Spanning Tree Protocol in a switched LAN?
  11. Difference between Spanning Tree Protocol (STP) and Rapid Spanning Tree Protocol (RSTP)?
  12. What is the STP blocking state?
  13. What is the STP Forwarding state?
  14. Difference between Root Port and Designated Port?
  15. What is the difference between path cost and root path cost?
  16. What is the difference between STP, MSTP, PVST and RSTP?
  17. What is path cost?
  18. Define selection criteria of STP root bridge.
  19. What are the four spanning tree port states?
  20. How do non root bridge decide which port will elect as root port?
  21. If a non root bridge has two redundant ports with the same root path cost, how does the bridge choose which port will be the root port?
  22. Port states of spanning tree protocol.
  23. If the users face delay during initial login, what you will suggest to implement?
  24. Why spanning tree BPDU filter is used?
  25. Can I use BPDU filter on trunk ports?
  26. Which port state is introduced by Rapid-PVST?
  27. What is Spanning Tree Protocol (STP) PortFast?
  28. What does STP do when it detects a topology change in the network due to a bridge or link failure?
  29. What is the reason for developing another version STP i.e. RSTP?
  30. Can STP be configured on a router?
  31. Is STP required to be configured when there is only one switch involved.
  32. Is a generic ethernet frame modified when STP is configured on the network
  33. How many designated ports can be available on a root bridge
  34. How many root bridges can be available on a STP configured network
  35. If the priority value of the two switches are same, which switch would be elected as the root bridge
  36. What is the basic purpose of the BPDUs and STA?
  37. What is Configuration BPDU?
  38. What is the destination MAC address used by Bridge Protocol Data Units (BPDUs)?
  39. What is TCN BPDU?
  40. What is TCA BPDU?
  41. What is Bridge Protocol Data Unit (BPDU) Frame Format?
  42. What is Path Cost or Spanning Tree Path Cost value?
  43. What is Root Port?
  44. What is Spanning Tree Port ID?
  45. What is PVST or PVST+?
  46. What is Extended System ID?
  47. What are STP Timers and Explain different types of STP Timers?

VLAN Interview Questions

  1. Which switching technology reduces the size of a broadcast domain?
  2. Which protocols are used to configure trunking on a switch?
  3. What is SVI ?
  4. what is meant by “router on stick” ?
  5. which is the default mode in switch ports ?
  6. Difference between 802.1Q and ISL ?
  7. Which are the two trunking protocols ?
  8. Which Protocol encapsulate Etherframes ?
  9. Which is the Vlan not tagged by 802.1Q ?
  10. How to delete vlan information from switch ?
  11. Difference between access and trunk mode ?
  12. Difference between dynamic auto and dynamic desirable ?
  13. what is the use of nonegociate command in switch ?
  14. Explain different switch port modes ?
  15. What is DTP ?
  16. Can we see trunk interfaces in show vlan command ?
  17. Which is the command used to see trunk interfaces ?
  18. What is the maximum number of vlans permitted in 802.1Q and ISL?
  19. what is the header size of 802.1Q ?
  20. How does a switch forward traffic from a trunk port to appropriate VLAN.
  21. Which feature would allow a VLAN to be sent untagged on a trunk port.
  22. Can two vlans be assigned with two subnets from the same major network.
  23. How does a switch forward traffic from a trunk port to appropriate VLAN.
  24. Is it necessary to add the VLAN tag devices to the SEA, or is it suffice to just have them defined within the Virtual Ethernet itself which is part of the SEA?
  25. On a multilayer Catalyst switch, which interface command is used to convert a Layer 3 interface to a Layer 2 interface?
  26. Which protocol reduces administrative overhead in a switched network by allowing the configuration of a new VLAN to be distributed to all the switches in a domain?
  27. What is the difference between an access port and a trunk port?
  28. What is Frame Tagging and different types of Frame Tagging?
  29. Explain difference between 802.1Q and ISL ?
  30. What is a Native VLAN and What type of traffic will go through Native VLAN?
  31. What is Inter-Vlan Routing?
  32. Two Switches are in VTP Server mode with different VLAN’s. Revision Number of both the switches is 0. Which switch will overwrite his own VLAN Database onto other, if both switches are in the same VTP Domain?
  33. If a Switch is in Client mode, Can we enter into the configuration mode ?

VTP Interview Questions

  1. What are different Vlan modes ?
  2. What happens to interfaces when you delete a VLAN?
  3. What is the difference between VTP Transparent and VTP Client mode ?
  4. Which is the default mode of VTP ?
  5. What is VTP Pruning ?
  6. What are two benefits of using VTP in a switching environment?
  7. Which VTP mode is capable of creating only local VLANs and does not synchronize with other switches in the VTP domain?
  8. What are the requirements to exchange VTP messages between two switches?

Wireless Interview Questions

  1. What is Wi-Fi?
  2. What is a Wi Fi Hotspot?
  3. What is IBSS, BSS and ESS ?
  4. Why WPA encryption is preferred over WEP?
  5. What is 802.1x and EAP ?
  6. Name two devices can interfere with the operation of a wireless network because they operate on similar frequencies?
  7. What are three basic parameters to configure on a wireless access point?
  8. What is the maximum data rate specified for IEEE 802.11b WLANs?
  9. Which encryption type does WPA2 uses ?
  10. When two laptops directly directed wirelessly,what type of topology has been created ?
  11. Which Spread spectrum technology does the 802.11b standard define for operation ?
  12. Which two wireless encryption method are based on RC4 encryption algorithm ?
  13. Which is the minimum parameter need on the access point inorder to allow a wireless client to operate on it ?
  14. What is the frequency range of the IEEE 802.11g standard?
  15. What is the maximum data rate for the 802.11a standard?
  16. What is the maximum data rate for the 802.11g standard?
  17. Can access point enabled with LWAPP, join the controller enabled with CAPWAP?
  18. Give an example of access point model, which can join only CAPWAP & one example which can join either of LWAPP or CAPWAP?
  19. When access point starts up, what will be the behavior in regards of LWAPP & CAPWAP?
  20. What are the basic guidelines for implementing CAPWAP?
  21. How to use USB console port on the Cisco 5500 wireless?
  22. How WLC works in terms of packet transfer or what is the mechanism?
  23. What is the master controller mode on WLC?
  24. What is the function of WLAN on WLC?
  25. How does DHCP work with the WLC?
  26. How do i change power & channels for a LAP?
  27. What happens to the wireless network when I perform a software upgrade? Do all the access points (APs) registered to a WLC go down until they are upgraded, or are they upgraded one at a time so that thewireless network can remain up?
  28. Can a Cisco IOS Software?based access point (AP) that has been converted to lightweight mode register with Cisco 4100 Series WLCs?
  29. Is it possible to go back and make corrections in the WLC configuration wizard at the time of the initial configuration?
  30. With the “ Management via Wireless” feature enabled on WLCs in a mobility group, I can only access one WLC from that mobility group, but not all. Why?
  31. Is it possible to assign an integrated controller in a 3750 Switch and a 4400 wireless LAN controller within the same mobility group?
  32. Are there any basic requirements to maintain when I use the mobilityanchor feature in order to configure wireless LAN controllers (WLCs) for guest access?
  33. If the WLCs in the same mobility group are separated by Network Address Translation (NAT) boundaries, can they communicate mobility messages with each other?
  34. Can we place the lightweight access point (LAP) under Network Address Translation (NAT)? Does LWAPP from access point (AP) to WLC work through NAT boundaries?
  35. Can I upgrade the WLC from one major version to another directly?
  36. How do I prevent loops on the WLC?
  37. Is there any way to recover my password for WLC?
  38. Why are our access points (APs) that are registered to other WLCs that are in the same RF group shown as rogues?

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