Understanding IP Addressing

• Computer networking involves the exchange of data between devices over a communication medium.
• IP Addressing is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.

IP Address Structure

• An IP address is a logical 32-bit address assigned to host.
• IP addresses are hierarchical and contain network and host information.
• IP addresses are represented in dotted decimal notation with four octets.
• Each octet ranges from 0 to 255.
• Example: 192.168.1.100 is a valid IPv4 address.

IPv4 Address Classes

• IPv4 addresses are divided into classes (A, B, C, D, and E) based on the first octet.
• Class A: 0-127 (First octet), supports large networks with many hosts.
• Class B: 128-191 (First octet), supports medium-sized networks.
• Class C: 192-223 (First octet), supports small networks with fewer hosts.
• Class D: 224-239 (First octet), used for multicast addressing.
• Class E: 240-255 (First octet), reserved for future use.

Private vs Public IP Addresses

• Public IP addresses are globally routable and used for communication over the internet.
• Private IP addresses are used within a private network and are not directly routable over the internet.
• Private IP address ranges:
  • 10.0.0.0 - 10.255.255.255 (Class A)
  • 172.16.0.0 - 172.31.255.255 (Class B)
  • 192.168.0.0 - 192.168.255.255 (Class C)
• Network Address Translation (NAT) is used to translate private IP addresses to public IP addresses for internet communication.

Subnetting

• Subnetting is the process of dividing a network into smaller, logical subnetworks.
• It helps optimize network performance, improve security, and manage IP address allocation.
• A subnet mask is used to distinguish the network and host portions of an IP address.
• A subnet mask is a 32-bit number, with contiguous ones from the left defining the network portion and contiguous zeros defining the host portion.
• Example: 255.255.255.0 indicates that the first three octets represent the network address and the last octet represents the host address.
• Classless Inter-Domain Routing (CIDR) notation is used to represent the subnet mask, e.g., /24 indicates a subnet mask of 255.255.255.0.

Address Resolution Protocol (ARP)

• ARP is a protocol used to map an IP address to a physical MAC address in a local network.
• When a device wants to communicate with another device on the same network, it sends an ARP request to determine the MAC address associated with the destination IP address.
• The device with the matching IP address responds with its MAC address.
• The sending device caches the IP-to-MAC address mapping in an ARP table for future communication.

Dynamic Host Configuration Protocol (DHCP)

• DHCP is a network management protocol used to automatically assign IP addresses and other network configuration parameters to devices on a network.
• DHCP eliminates the need for manual IP address configuration, reducing errors and simplifying network administration.
• DHCP operates using a client-server model.
• A DHCP server maintains a pool of IP addresses and leases them to DHCP clients.
• When a device connects to the network, it sends a DHCP Discover message to find a DHCP server.
• The DHCP server responds with a DHCP Offer message, proposing an IP address and other network configuration parameters.
• The client sends a DHCP Request message to accept the offered IP address.
• The DHCP server confirms the assignment with a DHCP Acknowledgment (ACK) message.
• DHCP Lease time: The duration for which an IP address is assigned to a device. The client must renew the lease before it expires to continue using the same IP address.

IPv6 Addressing

• IPv6 is the next-generation Internet Protocol designed to replace IPv4.
• IPv6 addresses are 128 bits long, providing a significantly larger address space than IPv4.
• IPv6 addresses are represented in hexadecimal notation, with eight groups of four hexadecimal digits separated by colons.
• Example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334 is a valid IPv6 address.
• Leading zeros in each group can be omitted.
• Consecutive groups of zeros can be replaced with a double colon (::), but only once in an address.
• IPv6 supports stateless address autoconfiguration (SLAAC), where devices can automatically configure themselves with a global IPv6 address without the need for a DHCP server.
• IPv6 includes built-in security features such as IPsec.
• IPv6 Header format has simplified header compared to IPv4 with no fragmentation field to improve routing efficiency.
• IPv6 supports new features such as Anycast addressing.