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    CDN:IPv6 address details

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    CDN:IPv6 address details

    Last Updated:Nov 15, 2025

    Introduction to IPv6

    IPv6 (Internet Protocol Version 6) is the sixth version of the Internet Protocol, designed to replace IPv4. An IPv6 address is 128 bits long. This provides approximately 3.4 × 10³⁸ addresses, a significant increase from the 32-bit address space of IPv4.

    IPv6 address format

    Basic format

    • An IPv6 address is represented as eight groups of four hexadecimal digits separated by colons (:).

    • Format: xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx

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

    Simplified notation

    Omit leading zeros

    Full format: 2001:0db8:0000:0042:0000:8a2e:0370:7334 
Simplified format: 2001:db8:0:42:0:8a2e:370:7334

    Compress consecutive zeros

    Full format: 2001:0db8:0000:0000:0000:0000:0000:0042 
Simplified format: 2001:db8::42

    Note: The double colon (::) can only be used once in an address.

    Special IPv6 addresses

    Address

    Description

    Purpose

    ::/128

    Unspecified address

    Equivalent to 0.0.0.0 in IPv4

    ::1/128

    Loopback address

    Equivalent to 127.0.0.1 in IPv4

    fe80::/10

    Link-local address

    Local network communication

    ff00::/8

    Multicast address

    One-to-many communication

    IPv6 CIDR block division

    Standard IPv6 address structure

    |-------- 48 bits --------|--- 16 bits ---|-------------- 64 bits --------------| 
| Global Routing Prefix   | Subnet ID     | Interface ID                      |

    Similar to IPv4, IPv6 uses a portion of the address to define subnets. The prefix length is specified after a slash (/).

    For example: 2001:0DB8:1234::/48

    The full representation of this address block is: 2001:0DB8:1234:0000:0000:0000:0000:0000/48

    The address range is:

    • Start address: 2001:0DB8:1234:0000:0000:0000:0000:0000

    • End address: 2001:0DB8:1234:FFFF:FFFF:FFFF:FFFF:FFFF

    Common subnet ID mapping table

    Decimal

    Hexadecimal

    Full notation

    Short form

    0

    0x0000

    2001:0DB8:1234:0000::/64

    2001:db8:1234::/64

    1

    0x0001

    2001:0DB8:1234:0001::/64

    2001:db8:1234:1::/64

    2

    0x0002

    2001:0DB8:1234:0002::/64

    2001:db8:1234:2::/64

    256

    0x0100

    2001:0DB8:1234:0100::/64

    2001:db8:1234:100::/64

    512

    0x0200

    2001:0DB8:1234:0200::/64

    2001:db8:1234:200::/64

    4096

    0x1000

    2001:0DB8:1234:1000::/64

    2001:db8:1234:1000::/64

    8192

    0x2000

    2001:0DB8:1234:2000::/64

    2001:db8:1234:2000::/64