What is an IP address, and how is it structured?

Last updated on Feb 5, 2024

Let's delve into more technical details about IP addresses:

Binary Representation:
- An IPv4 address is a 32-bit binary number.
- Example: 11000000101010000000000100000001
Dotted-Decimal Notation:
- To make it more human-readable, IPv4 addresses are expressed in dotted-decimal format.
- Example: 192.168.0.1
- Each octet (8 bits) is represented by a decimal number.
Classes (Historical):
- IPv4 originally had classes (A, B, C, D, E) with predefined network and host portions.
- Class A: 0.0.0.0 to 127.255.255.255
- Class B: 128.0.0.0 to 191.255.255.255
- Class C: 192.0.0.0 to 223.255.255.255
- Class D: 224.0.0.0 to 239.255.255.255 (Multicast)
- Class E: 240.0.0.0 to 255.255.255.255 (Reserved)
Subnetting and CIDR:
- Classful addressing is largely replaced by CIDR.
- CIDR allows more flexible allocation of IP addresses.
- Example CIDR notation: 192.168.0.0/24
Reserved Addresses:
- Some IP addresses are reserved for special purposes:
  - 127.0.0.1: Loopback (localhost)
  - 0.0.0.0: Unspecified address
  - 255.255.255.255: Broadcast (limited broadcast)

Binary Representation:
- IPv6 addresses are 128-bit binary numbers.
- Example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334
Hexadecimal Notation:
- IPv6 addresses are expressed in hexadecimal with colons separating each 16-bit group.
- Shortening consecutive groups of zeros is allowed (e.g., ::1 for 0000:0000:0000:0000:0000:0000:0000:0001).
Address Types:
- Global Unicast: Routable on the Internet.
- Link-Local: Used for communication on a single network segment.
- Site-Local (deprecated): Restricted to a specific site.
IPv4-Mapped Addresses:
- IPv6 can represent IPv4 addresses for compatibility.
- Example: ::ffff:192.168.0.1
Reserved Addresses:
- Similar to IPv4, IPv6 has reserved addresses, including the loopback (::1) and unspecified (::).
IPv6 Prefixes:
- IPv6 addresses include a prefix to denote the network and subnet.
- Example Prefix: 2001:0db8:85a3::/48