Top Essential 50 CCNA Interview Questions and Answers 2024

1. What is a VLAN?

Answer: A VLAN (Virtual Local Area Network) is a logical grouping of devices within a network, regardless of their physical location. It allows for the segmentation and isolation of broadcast domains.

2. What is the purpose of a router?

Answer Routers link different computer networks by forwarding data packets. In the OSI model, it belongs to the network layer.

3. What is the difference between a hub, a switch, and a router?

Answer Hub: Operates at the physical layer and simply broadcasts data to all connected devices. Switch: Operates at the data link layer, filters, and forwards data based on MAC addresses. Router: Operates at the network layer, and forwards data between different networks based on IP addresses.

4. What is OSPF?

Answer OSPF (Open Shortest Path First) is a dynamic routing protocol used to exchange routing information between routers within an autonomous system.

5. What is the purpose of NAT?

Answer NAT (Network Address Translation) is used to map private IP addresses to a single public IP address, allowing multiple devices within a private network to share a single public IP for internet access.

6. Explain the difference between TCP and UDP.

Answer TCP (Transmission Control Protocol) is connection-oriented, provides reliable and ordered delivery of data. UDP (User Datagram Protocol) is connectionless, provides faster but unreliable delivery of data.

7. What is ARP?

Answer ARP (Address Resolution Protocol) is used to map a known IP address to a MAC address in a local network.
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8. What is the purpose of the OSI model?

Answer The OSI (Open Systems Interconnection) model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven abstraction layers.

9. What is a subnet mask?

Answer An IP address is divided into network and host portions by a subnet mask, which is a 32-bit number. It identifies a host’s IP address and the network’s address.

10. Explain the concept of a default gateway.

Answer A default gateway is a router on a network that serves as an entry and exit point for data packets traveling between different networks.

11. What is a broadcast storm?

Answer A broadcast storm occurs when a network system is overwhelmed with continuous broadcast or multicast traffic, degrading network performance.

12. What is STP (Spanning Tree Protocol)?

Answer A bridged Ethernet local area network is guaranteed to maintain a loop-free topology by using STP.

13. What is the purpose of DHCP?

Answer DHCP (Dynamic Host Configuration Protocol) is used to dynamically assign IP addresses and other network configuration information to devices on a network.

14. Explain the difference between a collision domain and a broadcast domain.

Collision Domain: The set of devices on a network segment where collisions can occur. Broadcast Domain: The set of all devices that receive broadcast frames originating from any device within the group.

15. What is HSRP (Hot Standby Router Protocol)?

Answer HSRP is a Cisco proprietary redundancy protocol that provides high network availability by allowing two or more routers to work together in order to represent a single IP address for a particular network.
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16. What is the purpose of the TCP three-way handshake?

Answer To establish a reliable connection between two devices, the three-way handshake is used. It involves SYN, SYN-ACK, and ACK packets to synchronize sequence numbers.

17. What is the purpose of ACL (Access Control List)?

Answer An ACL is a set of rules applied to a router interface to control the traffic entering or exiting a network.

18. What is Layer 3 Switch

Answer A Layer 3 switch is basically a switch that can perform routing functions in addition to switching

19. What is VTP (VLAN Trunking Protocol)?

Answer VTP is a Cisco proprietary protocol used to manage VLAN configurations across a network of switches.

20. What is the purpose of the ping command?

Answer An Internet Protocol (IP) network uses the ping command to determine if a host is reachable and to measure the round-trip time of messages sent from a source host to a destination host.
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21. What is the role of ARP in a network?

Answer ARP (Address Resolution Protocol) is used to map an IP address to a MAC address in a local network.

22. Explain the concept of a MAC address.

Answer A MAC (Media Access Control) address is a unique identifier assigned to a network interface card (NIC) for communications at the data link layer of a network segment.

23. What is the purpose of the traceroute command?

Answer The traceroute command is used to trace the route that packets take to reach a destination, showing the IP addresses of routers along the way.

24. What is the purpose of the 802.1Q standard?

Answer The 802.1Q standard defines a protocol for carrying VLAN (Virtual Local Area Network) information over Ethernet networks.

25. What is the purpose of the BGP (Border Gateway Protocol)?

Answer The BGP protocol is a standardized exterior gateway protocol for exchanging routing and reachability information between autonomous systems (ASes).

26. What is DHCP snooping?

Answer DHCP snooping is a security feature that filters and regulates DHCP traffic within a network by monitoring and controlling the responses from DHCP servers.

27. Explain the purpose of the ARP cache.

Answer The ARP cache is a table that maps IP addresses to MAC addresses in a local network. It is used to store ARP (Address Resolution Protocol) information.

28. What is the purpose of the NAT/PAT?

Answer NAT (Network Address Translation) and PAT (Port Address Translation) are used to map private IP addresses to a public IP address, allowing multiple devices to share a single public IP for internet access.

29. What is the purpose of the subnetting?

Answer Subnetting is the process of dividing a larger network into smaller, more manageable sub-networks to improve performance and security.

30. What is the purpose of the VLAN trunking?

Answer VLAN trunking allows the transmission of VLAN information between switches, enabling devices on different switches to be part of the same VLAN.

31. What is the purpose of the loopback address?

Answer The loopback address (127.0.0.1) is used to test the network interface of a device. It allows a device to send and receive data to itself for diagnostic purposes.

32. What is RSTP (Rapid Spanning Tree Protocol)?

Answer RSTP is an enhancement of the Spanning Tree Protocol (STP) that provides faster convergence in the event of network topology changes.

33. What is EtherChannel?

Answer Ether Channel Combine bandwidth of multiple physical ports into a single logical Port known as a Port-channel The main purpose is to get more bandwidth and availability

34. What is the purpose of the GRE tunnel?

Answer GRE (Generic Routing Encapsulation) tunnels are used to encapsulate a wide variety of network layer protocols into point-to-point connections.

35. What is the purpose of the ACL (Access Control List)?

Answer An ACL is a set of rules used to filter network traffic and provide security by controlling access to network resources.

36. What is the purpose of the HSRP (Hot Standby Router Protocol)?

Answer HSRP is a Cisco proprietary protocol that provides high network availability by allowing two or more routers to work together to represent a single IP address for a particular network.

37. What is the purpose of the subnet mask?

Answer A subnet mask is used to divide an IP address into network and host portions, allowing for the creation of sub-networks.

38. Explain the concept of the broadcast storm.

Answer A broadcast storm occurs when a network is flooded with broadcast or multicast traffic, leading to network congestion and performance degradation.

39. What is Routingt?

Answer Routing is a process of establishing the routes that data packets take on their way to the destination. It is a process of selecting a path across one or more networks to move a data packet from source to destination.

40. What is the purpose of the VTP (VLAN Trunking Protocol)?

Answer VTP is a Cisco proprietary protocol used to manage VLAN configurations across a network of switches, simplifying VLAN administration.

41. What is the purpose of the STP (Spanning Tree Protocol)?

Answer STP is a network protocol that prevents loops in Ethernet networks by blocking redundant paths, ensuring a loop-free topology.

42. Explain the purpose of the NAT overload.

Answer NAT overload, also known as PAT (Port Address Translation), allows multiple devices in a private network to share a single public IP address by using different port numbers.

43. What is the purpose of the IPsec?

Answer IPsec (Internet Protocol Security) is a suite of protocols used to secure Internet Protocol (IP) communications by authenticating and encrypting each IP packet within a communication session.

44. What is the purpose of the subnetting?

Answer Subnetting is the process of dividing a larger network into smaller sub-networks to improve performance, security, and manageability.

45. What is the purpose of the VLAN pruning?

Answer VLAN pruning is a feature that allows a switch to dynamically prune or remove unnecessary VLANs from trunk links, reducing unnecessary traffic.

46. What is the purpose of the BGP (Border Gateway Protocol)?

Answer BGP is a standardized exterior gateway protocol used to exchange routing and reachability information between autonomous systems on the Internet.

47. Explain the concept of the OSI model.

Answer The OSI model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven abstraction layers, from physical to application.

48. What is the purpose of the EIGRP (Enhanced Interior Gateway Routing Protocol)?

Answer EIGRP is a Cisco proprietary routing protocol used to exchange routing information between routers within an autonomous system, providing fast convergence and efficient use of bandwidth.

49. What is the purpose of the default gateway?

Answer A default gateway is a router that is used when a device needs to communicate with a host on another network, serving as the exit point for traffic.

50. Explain the purpose of the TCP/IP model.

Answer The TCP/IP model is a conceptual framework that standardizes the functions of a telecommunication or computing system into four abstraction layers, from link to application. It is the basis for the Internet protocol suite.