3.3 IPv6 Addressing Explained
Key Concepts in IPv6 Addressing
- IPv6 Address Structure
- Types of IPv6 Addresses
- IPv6 Address Notation
1. IPv6 Address Structure
IPv6 addresses are 128-bit numbers, significantly larger than the 32-bit IPv4 addresses. This expanded address space allows for more unique identifiers, which is crucial for the growing number of devices connected to the internet. An IPv6 address is typically represented as eight groups of four hexadecimal digits, separated by colons.
Example: The IPv6 address 2001:0db8:85a3:0000:0000:8a2e:0370:7334 is structured into eight groups of four hexadecimal digits.
2. Types of IPv6 Addresses
IPv6 addresses can be categorized into several types, each serving a specific purpose:
- Unicast Addresses: Identify a single network interface. Examples include Global Unicast Addresses (similar to public IPv4 addresses) and Link-Local Addresses (used for communication within a single network segment).
- Multicast Addresses: Identify a group of interfaces, allowing a single packet to be sent to multiple recipients. This is similar to broadcasting in IPv4 but more efficient.
- Anycast Addresses: Identify a group of interfaces, but unlike multicast, only one member of the group receives the packet. This is useful for services like DNS where multiple servers can share an address, and the nearest or most available server responds.
Example: A Global Unicast Address might look like 2001:0db8::1, while a Link-Local Address might be fe80::1.
3. IPv6 Address Notation
IPv6 addresses can be written in various notations to make them easier to read and manage. Common notations include:
- Full Notation: All 128 bits are written out, such as
2001:0db8:85a3:0000:0000:8a2e:0370:7334. - Compressed Notation: Leading zeros in each group can be omitted, and consecutive groups of zeros can be replaced with double colons (::). For example,
2001:db8:85a3::8a2e:370:7334. - Mixed Notation: Combines IPv4 and IPv6 addresses, such as
::ffff:192.0.2.128.
Example: The address 2001:0db8:85a3:0000:0000:8a2e:0370:7334 can be compressed to 2001:db8:85a3::8a2e:370:7334.