Networking › Module 2 › Lesson 3
IPv6 Introduction
Why IPv6 exists, how addresses look, and what changes for security teams
Opening
We ran out of IPv4 addresses—so we built a bigger system
IPv4 gives about 4.3 billion addresses. That sounded huge in the 1980s. Today, every phone, IoT sensor, and cloud VM needs one. IPv6 uses 128-bit addresses—340 undecillion possibilities. It is not just "more numbers"—it changes how networks are designed and monitored.
1. IPv6 Address Format
IPv6 addresses are 128 bits, written as eight groups of four hexadecimal digits separated by colons: 2001:0db8:85a3:0000:0000:8a2e:0370:7334 Rules simplify them: Leading zeros in a group can be dropped: 0db8 becomes db8 One consecutive run of all-zero groups can be replaced with :: (only once per address) Short form: 2001:db8:85a3::8a2e:370:7334
2. Key Differences from IPv4
No NAT required (in theory)
Every device can have a globally unique address. NAT was an IPv4 workaround; IPv6 was designed for end-to-end connectivity.
Built-in IPSec support
IPv6 was designed with encryption and authentication in mind—though adoption of IPSec over IPv6 varies.
No broadcasts
IPv6 uses multicast and anycast instead. Neighbor Discovery (NDP) replaces ARP.
Dual stack is common
Most networks run IPv4 and IPv6 side by side during the transition. Your tools must handle both.
3. Security Implications
Attackers exploit IPv6 tunnels, rogue Router Advertisements, and NDP spoofing—similar to ARP attacks in IPv4. Many firewalls and IDS tools were built for IPv4 first, so IPv6 traffic can be overlooked or poorly filtered. Security teams must explicitly monitor IPv6, not assume it is disabled just because nobody talked about it.
Check if IPv6 is active on your machine
On Linux: ip -6 addr On Windows: ipconfig You may have a link-local address (fe80::...) even if you never configured IPv6 manually.
Knowledge Check
How many bits is an IPv6 address?
Multiple choice
Knowledge Check
What protocol replaces ARP in IPv6?
Multiple choice
Knowledge Check
True or False: Dual stack means running both IPv4 and IPv6 on the same network.
True or False