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Introduction to IPv6 Addressing

CCNA: 0 to Hero - Comprehensive Network Engineering Bootcamp

Lesson 18: Introduction to IPv6 Addressing

IPv6 was developed to overcome IPv4 address exhaustion. It is slowly being adopted in enterprise networks.

IPv6 Structure

  • IPv6 addresses are 128 bits long.
  • They are represented in hexadecimal notation, divided into eight 16-bit segments (called hextets), separated by colons (e.g., 2001:0DB8:ACAD:0001:0000:0000:0000:000A).

IPv6 Compression Rules

Due to their length, IPv6 addresses can be compressed:

  1. Rule 1: Omit Leading Zeros: Zeros at the beginning of any hextet can be dropped.
    • 0DB8 becomes DB8.
  2. Rule 2: Double Colon (::): A single contiguous string of all zero hextets can be replaced by a double colon (::). This can only be done once per address.

Example Compression:

2001:0DB8:0000:0000:0000:0000:0000:0001

  • Step 1: 2001:DB8:0:0:0:0:0:1
  • Step 2: 2001:DB8::1 (The standard shortened form).

Prefix Length

In IPv6, the subnet mask is always indicated by the prefix length (/x). The vast majority of IPv6 subnets use a /64 prefix, meaning the first 64 bits are for the Network/Subnet and the last 64 bits are for the Interface ID (Host).