CCNA | IPv4 Addressing | 8

Overview

  • Lecture 8 is a continuation of the discussion on IPv4 addresses, focusing on clarifying points from the previous lecture.

  • Topics Covered:

    • Quick review of IPv4 address classes

    • Calculation of maximum number of hosts

    • Network address, broadcast address, first usable address, and last usable address of networks

IPv4 Address Classes

  • IPv4 Address Classes: Divided into three main classes (A, B, C).

    • Class A:

      • Range: 1.0.0.0 to 126.255.255.255

      • Default Subnet Mask: 255.0.0.0 (prefix length /8)

    • Class B:

      • Range: 128.0.0.0 to 191.255.255.255

      • Default Subnet Mask: 255.255.0.0 (prefix length /16)

    • Class C:

      • Range: 192.0.0.0 to 223.255.255.255

      • Default Subnet Mask: 255.255.255.0 (prefix length /24)

  • Special Addresses:

    • 127.x.x.x range is reserved for loopback addresses and not counted in Class A.

Calculation of Maximum Addresses

  • Class C Example: 192.168.1.0/24

    • Last octet has 8 bits for the host portion: 0 to 255 = 256 total addresses.

    • Maximum usable addresses = 256 - 2 (network and broadcast addresses) = 254.

  • Class B Example: 172.16.0.0/16

    • Host portion has 16 bits: 0 to 65,535 = 65,536 total addresses.

    • Maximum usable addresses = 65,536 - 2 = 65,534.

  • Class A Example: 10.0.0.0/8

    • Host portion has 24 bits: 0 to 16,777,215 = 16,777,216 total addresses.

    • Maximum usable addresses = 16,777,216 - 2 = 16,777,214.

Usable Addresses Calculation

  • To find usable addresses, formula: 2^n - 2 (where n = number of host bits).

  • First Usable Address Calculation:

    • Class C: Network address 192.168.1.0 → First usable: 192.168.1.1

    • Class B: Network address 172.16.0.0 → First usable: 172.16.0.1

    • Class A: Network address 10.0.0.0 → First usable: 10.0.0.1

  • Last Usable Address Calculation:

    • Class C: Broadcast address 192.168.1.255 → Last usable: 192.168.1.254

    • Class B: Broadcast address 172.16.255.255 → Last usable: 172.16.255.254

    • Class A: Broadcast address 10.255.255.255 → Last usable: 10.255.255.254

Cisco Router Configuration

  • Demonstrated configuration of a Cisco router with IP addresses:

    • Three networks connected to a single router (R1).

    • R1's Interface Configuration:

      • Gigabit Ethernet 0/0: Assigned 10.0.0.254 (/8)

      • Gigabit Ethernet 0/1: Assigned 172.16.255.254 (/16)

      • Gigabit Ethernet 0/2: Assigned 192.168.0.254 (/24)

    • Commands:

      1. enable: to enter privileged exec mode

      2. show ip interface brief: checks interface IPs and status

      3. int g0/0: Entering interface configuration mode

      4. Assigning IP address with ip address command followed by no shutdown command to enable interface.

Useful Show Commands

  • show ip interface brief: Overview of all interfaces, their IPs, and status.

    • Displays if the interfaces are up or down.

  • show interfaces: Detailed view of interfaces' layer 1 and layer 2 status, including MAC addresses.

  • show interfaces description: Displays status, protocol, and optional descriptions of each interface for easier identification.

Recap

  • Covered IPv4 address classes and their configurations.

  • Discussed methods to calculate the maximum, first usable, and last usable addresses.

  • Demonstrated Cisco router configurations and useful commands to manage interfaces.

  • Encouraged review of material before proceeding to the quiz.