CCNA Class 05: IPv4 and IPv6 Addresses Introduction
History of IP Addresses
In the 1960s, the Internet was born from a research network called ARPANET i.e. a computer network founded by the Advanced Research Projects Agency of the U.S. Department of Defense. ARPANET was created to enable communication between computers at various research institutions. However, a standardized addressing system was needed to identify each device and manage traffic on this growing network.
In the early 1970s, the TCP/IP protocol suite was developed and In 1974, with the key paper published by Vint Cerf and Bob Kahn namely "A Protocol for Packet Network Intercommunication". TCP/IP became the standard for ARPANET and was foundational to modern networking. Internet Protocol (IP) was one of these protocols, providing a structured addressing system. The addressing scheme implemented was IPv4, which introduced a 32-bit address space, allowing for approximately 4.3 billion unique addresses (232).
In the 1981s, Introduced the Classful IPv4 address and divided into five classes -
Class A: Large networks, with millions of addresses (1-126)
Class B: Medium-sized networks (128-191)
Class C: Small networks, with fewer addresses (192-223)
Class D: Reserved for multicasting (224-239)
Class E: Reserved for future or experimental use (240-255)
In the 1993s, Introduced the CIDR Notation (Classless Inter-Domain Routing) for optimizing the IP address allocation of networks in an organization.
Late 1990s, Introduced the following two technologies to manage the IP address.
NAT (Network Address Translation): All of the Private IP addresses traverse to the internet by single Public IP address.
Private IP Address Ranges: Certain IP ranges (e.g., 192.168.x.x, 10.x.x.x) were designated for use within private networks only, reducing the demand for public IPs.
In the 1998s, Introduced the IPv6 for recovering the limitations of IPv4. It uses a 128-bit address format, An IPv6 address is represented in hexadecimal notation (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334).
From the 2000 to Present, Dual-stack IPv4/IPv6 coexists, with gradual IPv6 adoption.
Understanding the IP Address Classes
An IPv4 address is a 32-bit number, divided into four 8-bit segments called octets. Each octet is separated by a period (dot-decimal format), like 192.168.1.1. The address space is divided based on bit values in the address.
Class A (Large Networks)
Range: 1.0.0.0 to 126.255.255.255
Default Subnet Mask: 255.0.0.0
First Bit Pattern: Starts with 0 (first octet between 1-126)
Network/Host Bits: 8 bits for network, 24 bits for hosts
Total Networks: 128 networks
Hosts per Network: 16,777,214 (over 16 million addresses per network)
Use: Class A is designed for very large organizations or networks with a massive number of devices.
Class B (Medium-Sized Networks)
Range: 128.0.0.0 to 191.255.255.255
Default Subnet Mask: 255.255.0.0
First Bit Pattern: Starts with 10 (first octet between 128-191)
Network/Host Bits: 16 bits for network, 16 bits for hosts
Total Networks: 16,384 networks
Hosts per Network: 65,534 (over 65,000 addresses per network)
Use: Class B addresses are allocated to medium-sized organizations or university campuses with a substantial number of devices.
Class C (Small Networks)
Range: 192.0.0.0 to 223.255.255.255
Default Subnet Mask: 255.255.255.0
First Bit Pattern: Starts with 110 (first octet between 192-223)
Network/Host Bits: 24 bits for network, 8 bits for hosts
Total Networks: 2,097,152 networks
Hosts per Network: 254 (small number of addresses per network)
Use: Class C is designed for small networks, such as local area networks (LANs), where fewer than 254 devices need unique IP addresses.
Class D (Multicasting)
Range: 224.0.0.0 to 239.255.255.255
First Bit Pattern: Starts with 1110 (first octet between 224-239)
Use: Class D is reserved for multicast groups, where data is sent to multiple specific hosts simultaneously (e.g., video streaming or teleconferencing).
Class E (Experimental)
Range: 240.0.0.0 to 255.255.255.255
First Bit Pattern: Starts with 1111 (first octet between 240-255)
Use: Class E addresses are reserved for experimental or future use and are not used in public networking.
Special IPv4 Addresses
Private IP Address
Class A: 10.0.0.0 to 10.255.255.255
Class B: 172.16.0.0 to 172.31.255.255
Class C: 192.168.0.0 to 192.168.255.255
Loopback Address: 127.0.0.1 (typically used as localhost), allowing a device to communicate with itself.
APIPA:
Automatic Private IP Addressing
Range: 169.254.0.1 - 169.254.255.254
Subnet Mask: 255.255.0.0.
Summary of the IP Address
IPv6 Introduction and its Classifications
IPv6 (Internet Protocol version 6) is the most recent version of the Internet Protocol (IP), which is designed to address limitations in the previous version-IPv4. IPv6 was developed primarily to resolve the issue of IPv4 address exhaustion and to improve features related to routing, security, and overall efficiency.
Here’s a comprehensive look at IPv6, including the Introduction and Classification of addresses.
Introduction to IPv6
IPv6 was developed by the Internet Engineering Task Force (IETF) and was introduced as a successor to IPv4 to address the finite number of IPv4 addresses (about 4.3 billion unique addresses). IPv6 uses 128-bit addresses, allowing for a vastly larger address space, theoretically up to approximately 3.4X1038 Unique addresses.
For example, 2001:0db8:85a3:0000:0000:8a2e:0370:7334
Here, An IPv6 address has eight groups of four hexadecimal digits (16 bits per group), for a total of 128 bits. The address can also be abbreviated by omitting leading zeros and using double colons (::) to represent consecutive groups of zeroes (only once per address). Ex - 2001:db8:85a3::8a2e:370:7334
IPv6 Address Structure -
Ex-01: IPv6 Address Structure Format
Ex-02: Applying Zero Compression
IPv6 Address Classification
The main types of IPv6 addresses are -
Unicast Addresses
Purpose: Identifies a single unique device on a network.
Types:
Global Unicast: These are globally routable addresses, similar to public IPv4 addresses. They start with the prefix 2000::/3.
Unique Local Unicast: It is not intended to be routed on the global internet, but are routable within a limited area. Private IP address as like IPv4. The prefixes are FC00::/7 & Fd00::/8
Link-Local Unicast: Used for communication within a single network segment (e.g., on the same link or network). It's similar with APIPA of IPv4. These addresses start with FE80::/10.
Multicast Addresses
Purpose: Allows a packet to be sent to multiple devices simultaneously.
Prefix: FF00::/8
Anycast Addresses
Define: One IP, Multiple Servers.
Purpose: Allows packets to be delivered to any one of a group of interfaces that share the same IPv6 address.
Special IPv6 Addresses
Loopback Address: 0:0:0:0:0:0:0:1 equals ::1/128. Equivalent to 127.0.0.1 in IPv4, this address is used to identify the local interface.
Unspecified Address: 0:0:0:0:0:0:0:0 equals ::/128. Represents an absence of address (similar to 0.0.0.0 in IPv4) and is used during the initial phase of auto-configuration.
Key Comparison between IPv4 and IPv6
