OSI - Layer 3: IP Addressing

OSI - Layer 3: IP Addressing

• IP addressing is fundamental for devices to communicate on a network
• Every connected device has a unique IP address
• Two main versions of IP addresses exist:
  • IPv4: 32-bit address, represented as four decimal numbers separated by dots (e.g., 192.168.0.1)
  • IPv6: 128-bit address, represented as groups of hexadecimal digits separated by colons (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334)

Learning Objectives

• Understand the structure and components of an IPv4 address
• Master IPv4 address classes
• Differentiate between public and private IP addresses
• Use CIDR notation to define subnets
• Apply subnetting to divide a network

Introduction

• IPv4 addresses identify every machine connected to a computer network
• IPv4 addresses consist of four octets, each with a decimal value between 0 and 255, separated by dots
• Example: 172.16.254.1

IPv4 Addresses

• A 32 bit address (4 bytes)
• Example: 172.16.254.1
• IPv4 addresses structure is divided into two parts:
  • Network address: Identifies the network. Used to route data packets to the correct network
  • Host address: Identifies the specific device on that network.

IP Address Classes

• IPv4 addresses are divided into classes (A, B, C, D, E)
• Classes A, B, and C are used for public networks
• Class A:
  • Address range: 0.0.0.0 to 127.255.255.255
  • Use: Large organizations with many hosts on few networks
  • Example address: 10.0.0.1 (network 10.0.0.0)
• Class B:
  • Address range: 128.0.0.0 to 191.255.255.255
  • Use: Medium-sized organizations with moderate number of hosts
  • Example address: 172.16.0.1 (network 172.16.0.0)
• Class C:
  • Address range: 192.0.0.0 to 223.255.255.255
  • Use: Small networks with limited number of hosts
  • Example address: 192.168.1.1 (network 192.168.1.0)

IP Address Classes (Advanced)

• Classes D (multicast), and E (reserved)
• Special Addresses:
  • 127.0.0.1: Loopback address (localhost)
  • 255.255.255.255: Limited broadcast address
• APIPA (Automatic Private IP Addressing): used when a DHCP server is unavailable

Subnet Mask

• Isolates bits that belong to the network part of an IP address
• Typically done using binary representation of the IP address and the subnet mask, performing a logical AND operation
• Determines the network and host portions

CIDR Notation

• Used to specify how many bits are reserved for the network part of an IP address
• Example: 10.80.96.11/22

Number of hosts in a Network

• Calculate the number of bits allocated for the host portion
• Calculates the number of usable IP addresses
• Calculate the usable IP addresses, Hosts IP range

Subnetting

• Dividing a network into smaller subnetworks by adjusting the subnet mask
• Optimizes the use of IP addresses
• Logically segments networks to manage traffic and security

IPv6 Addresses

• 128-bit address space
• Written in hexadecimal notation, separated by colons
• Example: 2001:0db8:00f4:0845:ea82:0627:e202:24fe
• Three types
  • Unicast
  • Multicast
  • Anycast
• Various addressing schemes for private use
• Techniques to support coexistence between IPv4 and IPv6:
  • Dual Stack
  • Tunneling
  • Address Translation (NAT64)

Conclusion

• IPv4 and IPv6, public vs private addresses, and subnetting are crucial for network administration