Jeremy's IT Lab: CCNA Subnetting Lecture

Introduction

• Free course for CCNA.
• Importance of subnetting for network engineers and CCNA exam.
• Subnetting tutorial split into 2-3 videos for clarity.
• Simplicity emphasized, avoiding over-complication.

Topics Covered

1. CIDR (Classless Inter-Domain Routing)

   • Introduces flexibility in IPv4 addressing compared to traditional class A, B, C.

2. IPv4 Address Classes Review

   • Class A:
     • First octet begins with 0, range 0-127.
     • /8 prefix length.
   • Class B:
     • First octet begins with 10, range 128-191.
     • /16 prefix length.
   • Class C:
     • First octet begins with 110, range 192-223.
     • /24 prefix length.
   • Class D:
     • First octet begins with 1110, range 224-239.
   • Class E:
     • First octet begins with 1111, range 240-255.

3. Subnetting Process

   • Step-by-step guide to subnetting to avoid confusion.

Purpose and Need for CIDR

• Traditional classful addressing leads to wasted IP addresses.
• Examples of waste:
  • Point-to-point networks using entire /24 networks.
  • Allocating a class B network for 5000 hosts, wasting ~60,000 addresses.
• IETF introduced CIDR in 1993 to address the inefficiencies.

CIDR and Subnetting

• CIDR allows smaller subnets by removing rigid class rules:

  • Example: Using /30 or /31 instead of /24 for point-to-point connections.

• Subnetting Calculations:

  • Formula: 2^number of host bits - 2 (minus network and broadcast addresses).
  • Practice with varying prefix lengths:
    • /30: 2 usable addresses, ideal for point-to-point with 0 wasted.
    • /31: Special case for point-to-point, using both addresses.
    • /32: Used for specific host routes.

Example Scenario

• Given 192.168.1.0/24 network with 4 subnets needed for 45 hosts each.
• Calculating subnet sizes:
  • /26 subnet chosen as it supports 62 usable addresses.

Summary

• CIDR enhances flexibility and efficiency in IP addressing.
• Subnetting basics covered with emphasis on avoiding waste.
• Encouragement to practice subnetting with quiz hints.

Additional Resources

• Flashcards for review.
• Membership options for supporting the channel.
• Call to subscribe, like, comment, and share.