IPv6 Addressing

IPv6 Addressing is the system used to assign unique identifiers to devices on an IPv6-based network. IPv6 (Internet Protocol version 6) was developed to replace IPv4 (Internet Protocol version 4) due to the limited number of available IPv4 addresses. IPv6 provides a much larger address space and is designed to address the growing need for internet-connected devices.

Key Points:

IPv6 Address Structure:

An IPv6 address is a 128-bit number, divided into eight 16-bit blocks, each represented as four hexadecimal digits (0-9, A-F).

The general format of an IPv6 address is written as 8 groups of 4 hexadecimal digits separated by colons. For example:

2001:0db8:85a3:0000:0000:8a2e:0370:7334

Example:

2001:0db8:85a3:0000:0000:8a2e:0370:7334

Abbreviating IPv6 Addresses:

Leading Zeros: In each 16-bit block, leading zeros can be omitted. For example, 0001 can be written as 1.

Consecutive Blocks of Zeros: A series of consecutive blocks of zero can be replaced with ::, but this can only be done once in an address.

Example:

Full address: 2001:0db8:0000:0000:0000:0000:0000:0020

Abbreviated: 2001:0db8::20

Types of IPv6 Addresses:

Unicast: Refers to a one-to-one communication between a single sender and a single receiver. Example: 2001:0db8::1.

Multicast: Refers to one-to-many communication, where data is sent from one sender to multiple receivers. Example: FF00::/8.

Anycast: Refers to one-to-nearest communication, where data is sent to the nearest device in a group. Example: 2001:0db8::/32.

Global and Link-Local Addresses:

Global Unicast Addresses (GUAs): These are globally routable addresses similar to public IPs in IPv4. They are assigned by an address allocation authority and can be routed across the internet. Example: 2001:0db8::/32

Link-Local Addresses: These are used for communication within a local network (link) and are not routable beyond the local network. They start with the prefix fe80::/10. Example: fe80::1

IPv6 Address Prefixes:

Subnet Prefix: Like IPv4, IPv6 networks are divided into subnets using a prefix. For example, 2001:0db8:1234::/48 specifies a subnet of IPv6 addresses.

Subnet Mask: The prefix length (after the /) indicates the size of the network. For example, /64 is the most common subnet size for IPv6 networks, indicating the first 64 bits are used for network addressing.

IPv6 Addressing Example:

Scenario: A company uses IPv6 for its internal network. The company has been allocated the block 2001:0db8:abcd::/48 by their ISP.

Global Unicast Address: An address like 2001:0db8:abcd:0001::1 can be assigned to a server, which is globally reachable.

Link-Local Address: A computer in the same network might have the address fe80::1, which is used for communication within the local network but cannot be routed across the internet.

Multicast Address: A multicast address such as FF02::1 is used to communicate with all devices on the local network.