Network Engineering Lecture: Top 20 CCNA Interview Questions

Introduction

• Presenter: Amar
• Focus: CCNA level interview questions and answers
• Part 1 covers questions 1-10

Question 1: What is the OSI Model?

• OSI Model: A reference model for network protocols
• Developed By: ISO in 1984
• Structure: Seven-layer architecture
• Layers:
  1. Physical Layer
  2. Data Link Layer
  3. Network Layer
  4. Transport Layer
  5. Session Layer
  6. Presentation Layer
  7. Application Layer
• Memory Aid: "Please Do Not Tell Sales People Anything"
  • P: Physical
  • D: Data Link
  • N: Network
  • T: Transport
  • S: Session
  • P: Presentation
  • A: Application

Question 3: What is an IP Address?

• Definition: Address of a device for communication
• Versions: IPv4 and IPv6
  • IPv4: 32-bit address (e.g., 192.10.8.0.1)
  • IPv6: 128-bit address
• Purpose: Identifies devices for communication over a network

Question 4: Difference Between Hub, Switch, and Router

• Hub:
  • Layer 1 device
  • Connects multiple devices in LAN
  • Operates at Physical Layer
  • Considered a "dumb" device
• Switch:
  • Layer 2 device
  • Uses MAC addresses for communication
  • Operates at Data Link Layer
• Router:
  • Layer 3 device
  • Uses IP addresses for routing
  • Connects different networks

Question 5: What is RJ45?

• Type: Connector used for Ethernet cables
• Purpose: Common in network cabling

Question 6: What is DNS?

• DNS: Domain Name System
• Function: Translates domain names into IP addresses
• Example: Resolving facebook.com into an IP address
• Benefit: Allows easier access to websites by human-readable names

Question 7: What is Routing?

• Definition: Process of forwarding packets from one network to another
• Performed by: Routers using routing tables
• Types of Routing:
  1. Default Routing
  2. Static Routing
  3. Dynamic Routing
• Dynamic Routing: Automatic path selection using protocols

Question 8: What is Ping?

• Purpose: Tests Layer 3 reachability of a host
• Functionality:
  • Sends packets to a destination and checks for replies
  • Measures latency and packet loss
• Example: Pinging google.com, showing average latency and packet success

Question 9: What is AD Value?

• AD Value: Administrative Distance; measures trustworthiness of routing protocols
• Lower AD Value: More trusted route
• Range: 0 (most trusted) to 255 (not used)

Question 10: AD Value of OSPF

• OSPF AD Value: 110
• Comparison with Other Protocols:
  • Directly connected: 0
  • Static: 1
  • External BGP: 20
  • Internal BGP: 200
  • EIGRP: 90
  • RIP: 120
  • Unknown: 255

Conclusion

• The video will continue with questions 11-20 in the next part.
• Emphasis on remembering AD values and OSI layers for interviews.