🌎 IPv6 (The Easy Version)

IPv6 — Full Notes

Why Was IPv6 Created?

IPv4 uses 32-bit addresses, which provides about 4.3 billion unique addresses.

As the Internet grew, the number of connected devices exploded:

• 📱 Smartphones

• 💻 Computers

• 🎮 Gaming consoles

• 📷 Security cameras

• 💡 Smart home devices (IoT)

• 🚗 Connected vehicles

• 🌐 Billions of Internet-connected devices

Because IPv4 addresses were running out, IPv6 was created.

IPv6

• 128-bit addresses

• About 340 undecillion addresses

• Designed to support the future growth of the Internet

Memory Trick

IPv4 = Running out of addresses
IPv6 = Practically unlimited addresses

Section Break Down:

• IPv4 has 32 bits

• IPv6 has 128 bits

IPv6 Address Format

IPv4

192.168.1.10

Uses:

• 
  Decimal numbers
  

• 
  Periods (.)
  

IPv6

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

Uses:

• 
  Hexadecimal
  

• 
  Colons (:)
  

Section Breakdown

• IPv4 looks like this 192.168.1.10

• IPv6 looks like this 2001:0db8:85a3:0000:0000:8a2e:0370:7334

Hexadecimal

IPv6 uses hexadecimal (base 16) instead of decimal.

Hexadecimal includes:

0 1 2 3 4 5 6 7 8 9 A B C D E F

Where:

A = 10
B = 11
C = 12
D = 13
E = 14
F = 15

IPv6 Has 8 Groups

Example:

1    2    3    4    5    6    7    8

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

Each address contains:

• 8 groups
  

• 4 hexadecimal digits per group
  

Shortening IPv6 Addresses

Network+ loves these rules.

Rule #1 — Remove Leading Zeros

You may remove zeros at the beginning of a group.

Example:

0db8

becomes

db8

Another:

0007

becomes

7

❌ Don't remove zeros from the end.

Rule #2 — Replace Consecutive Zero Groups with ::

Example:

Before:

2001:0db8:0000:0000:0000:0000:0000:0001

After:

2001:db8::1

Important

You may use :: only once in an IPv6 address.

Why?

Because using it twice would make it impossible to know how many groups of zeros were removed.

⭐ Network+ Exam Tip

If you see an address using :: twice, it's invalid.

Common IPv6 Address Types

Global Unicast

• Global Unicast = Public Internet and starts with 2xxx or 3xxx

Starts with:

2xxx

or

3xxx

Example:

2001:db8::1

Used for:

• 
  Public Internet communication
  

Think:

Global = Public Internet

More about Global Unicast

Imagine the Internet is like the postal system.

• Your house = your device

• Your address = your IP address

• The roads = the Internet

Global Unicast Address = Your Home Address 🏠

A Global Unicast IPv6 address is a public address that can be reached from anywhere on the Internet (assuming firewalls allow it).

For example:

2001:db8::1

It starts with 2 or 3, so you immediately know:

🌍 "This is a public IPv6 address."

Real-Life Example

Suppose you open YouTube.

Your computer might have this IPv6 address:

2001:abcd:1234::50

The YouTube server has another Global Unicast address.

Because both devices have public IPv6 addresses, they can communicate across the Internet.

💻 Your PC
2001:abcd:1234::50
        │
        │ Internet 🌍
        │
📺 YouTube Server
2001:4860:....

Compare It to IPv4

IPv4 has:

• Public IP: 8.8.8.8
  

• Private IP: 192.168.1.10
  

IPv6 has:

• Global Unicast (Public): 2001:...
  

• Unique Local (Private): fd00:...
  

So think of it like this:

Why do they start with 2 or 3?

IPv6 addresses are grouped into ranges.

If the first hexadecimal digit is:

• 2 → Global Unicast
  

• 3 → Global Unicast
  

Examples:

2001:db8::1   ✅ Global Unicast
2607:f8b0::1  ✅ Global Unicast
3001:abcd::5  ✅ Global Unicast

As soon as you see an address starting with 2 or 3, you should think:

🌍 "This is a public IPv6 address that can communicate over the Internet."

Easy Memory Trick 🧠

2 or 3
   ↓
🌍 Global
   ↓
🌐 Public Internet

So whenever you see:

2001:db8::1

Don't worry about the rest of the address yet. Just recognize the first digit (2) and think:

"This is a Global Unicast address—a public IPv6 address, like a public IPv4 address."

Link-Local

• Link-local is IPV6 and means used for communication of devices within the same local network only. Starts with FE80::

Brief Description

Link-Local: An IPv6 address used for communication with devices on the same local network only.

Easy Memory Trick 🧠

• Link = the network you're directly connected to.

• Local = doesn't leave that network.

Think:

💻 Your PC «- » 🖨 Printer
(Same network)

Starts with:

FE80::

Automatically assigned to every IPv6 device.

Used only on the local network.

Routers do not forward link-local addresses.

You'll commonly see them when using:

• 
  ipconfig
  

• 
  ip a
  

• 
  ifconfig
  

Think:

Link-local = Only talks to nearby devices

Unique Local Address (ULA)

Starts with:

FC

or

FD

Private IPv6 addresses.

Similar to:

192.168.x.x

in IPv4.

Think:

Unique Local = Private Network

Loopback

::1

Equivalent to:

127.0.0.1

Represents:

"This computer."

IPv4 vs IPv6

Broadcast, Multicast, and Anycast

Broadcast (IPv4)

Broadcast sends a packet to every device on the local network.

Think:

"Everyone listen!"

Multicast (IPv6)

Multicast sends traffic only to devices that joined a specific group.

Think:

"Only this group listen."

Examples:

• 
  Routers
  

• 
  Printers
  

• 
  Servers
  

Anycast (IPv6)

Multiple devices share the same address.

Traffic is automatically delivered to the closest or best destination.

Think:

"Take me to the nearest server."

Easy Memory Tricks

IPv4

• 
  32 bits
  

• 
  4 octets
  

• 
  Dots
  

Think:

4 → 32 → Dots

IPv6

• 
  128 bits
  

• 
  8 groups
  

• 
  Colons
  

Think:

128 → 8 → Colons

⭐ Network+ Summary

Remember these:

✅ IPv4 = 32 bits

✅ IPv6 = 128 bits

✅ IPv6 uses hexadecimal

✅ IPv6 uses colons (:)

✅ IPv6 has 8 groups

✅ Remove leading zeros

✅ :: can only appear once

✅ ::1 = Loopback

✅ FE80:: = Link-local

✅ FC/FD = Unique Local (private)

✅ 2xxx/3xxx = Global Unicast (public)

✅ IPv6 does not use broadcast

✅ IPv6 uses multicast and anycast

✅ NAT is generally not required with IPv6

🚨 Network+ Exam Traps

❌ Trap: IPv6 uses decimal numbers.

✅ Correct: IPv6 uses hexadecimal (0–9, A–F).

❌ Trap: IPv6 uses periods.

✅ Correct: IPv6 uses colons.

❌ Trap: You can use :: multiple times.

✅ Correct: Only once per IPv6 address.

❌ Trap: FE80:: is a public address.

✅ Correct: FE80:: is a link-local address.

❌ Trap: ::1 is a network address.

✅ Correct: ::1 is the loopback address.

❌ Trap: IPv6 uses broadcast.

✅ Correct: IPv6 uses multicast and anycast instead.

📚 Flashcards

Why was IPv6 created?

➡ IPv4 ran out of addresses.

How many bits does IPv6 use?

➡ 128 bits.

What number system does IPv6 use?

➡ Hexadecimal.

What separator does IPv6 use?

➡ Colons (:).

How many groups are in an IPv6 address?

➡ 8.

What does :: do?

➡ Compresses consecutive groups of zeros.

How many times can :: appear?

➡ Once.

What is the IPv6 loopback address?

➡ ::1.

What prefix identifies a link-local address?

➡ FE80::.

What prefix identifies a Unique Local Address (ULA)?

➡ FC:: or FD::.

What prefix identifies a Global Unicast address?

➡ 2xxx or 3xxx (2000::/3).

Does IPv6 use broadcast?

➡ No.

What replaces broadcast in IPv6?

➡ Multicast and Anycast.

Is NAT generally needed with IPv6?

➡ No.