Ipv6

IPv6 Addressing — CCNA 200-301 Study Lesson IPv6 is a guaranteed topic in the Network Fundamentals domain (20%) and also appears in IP Connectivity when IPv6 static routing is tested — understanding address types, notation rules, and auto-configuration methods is essential for both multiple-choice and scenario questions. --- ## Why IPv6 Exists The exhaustion of IPv4's roughly 4.3 billion addresses drove the adoption of IPv6, which uses 128-bit addresses providing an astronomically larger address space. Rather than replacing IPv4 overnight, networks run both simultaneously — a concept called dual-stack. --- ## IPv6 Address Notation IPv6 addresses are written as eight groups of four hexadecimal digits, separated by colons: `` 2001:0DB8:0000:0000:0000:0000:0001:0002 ` ### Two Simplification Rules Rule 1 — Drop leading zeros within any group: ` 2001:DB8:0:0:0:0:1:2 ` Rule 2 — Double-colon (::) compression replaces one or more consecutive all-zero groups (used only once per address): ` 2001:DB8::1:2 ` > ⚠️ The :: can only appear once in an address. If used twice, the router cannot determine how many zero groups each :: represents. --- ## IPv6 Address Types You Must Know | Address Type | Prefix / Range | Purpose | |---|---|---| | Global Unicast Address (GUA) | 2000::/3 | Routable on the internet; equivalent to IPv4 public addresses | | Link-Local Address (LLA) | FE80::/10 | Required on every IPv6-enabled interface; used for neighbor discovery and routing protocol hellos; never routed beyond the local link | | Loopback | ::1/128 | Local loopback; equivalent to IPv4 127.0.0.1 | | Unspecified | ::/128 | Source address before a device has an address (like 0.0.0.0 in IPv4) | | Unique Local | FC00::/7` | Private, non-routable; roughly equivalent to RFC…