IPv6 Address Types

IPv6 is divided into several address types in networking.

Each IPv6 Address Types has a distinct purpose. Some identify a single device, others reach entire groups.
Before configuring anything, it is essential to understand the full picture of how these address types are organized.

Figure 1 - IPv6 address types

IPv6 divides its address space into three main categories: Unicast for one-to-one communication, Multicast for one-to-many, and Anycast for one-to-nearest.

By the end of this lesson, you will know exactly which type to use, when to use it, and how each behaves in real networks.

Unicast addresses are the most common type of IPv6 addresses. They identify a single interface on a device, meaning that packets sent to a unicast address are delivered to one specific destination.
This represents a one-to-one communication model, which is the foundation of most IPv6 traffic.

Figure 2 - Unicast traffic: packets go directly from one device to another.

IPv6 defines several unicast address types, each with a specific purpose.

Figure 3 – IPv6 Unicast Addresses

You’ll encounter Global Unicast, Link-Local, Unique Local, Loopback, Unspecified, and Embedded IPv4 addresses.
Let’s start with the most common type used across global networks.

Global Unicast Addresses

Global Unicast addresses are the IPv6 equivalent of public IPv4 addresses.
They are globally unique and routable across the Internet, allowing direct communication between devices in different networks.

Let’s look at an example together in Figure 4 to see how a Global Unicast address is structured.

Figure 4 - IPv6 Global Unicast Address Breakdown

This address is divided into three parts that you should remember:

• The Global Prefix (48 bits) — assigned by your ISP to identify your network on the Internet,

• The Subnet ID (16 bits) — the part you’ll use to organize and create your internal subnets,

• The Interface ID (64 bits) — which identifies the exact host or interface within that subnet.

Configure Global Unicast Address

Now, let's configure a global unicast address on a router.

R1# conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)# interface G0/0
R1(config-if)# ipv6 address 2001:41B1:1234:1::1/64
R1(config-if)# no shutdown
R1(config-if)# end

Now verify it:

R1# show ipv6 interface brief
GigabitEthernet0/0    [up/up]
  FE80::A8BB:CCFF:FE12:3401
  2001:41B1:1234:1::1

Here you can clearly see:

• The Link-Local address (FE80::)

• The Global Unicast address (2001:41B1:1234:1::1)

That’s how IPv6 addresses appear on a real router.

Next, let’s look at the addresses that every IPv6 interface generates automatically.

Link-Local Addresses

Link-Local addresses are automatically generated on every IPv6-enabled interface.
They are used for communication within the same local network segment and are not routable beyond it.

Figure 5 - IPv6 Link-Local Address Breakdown

By default, the Interface ID portion is generated automatically (often using EUI-64 based on the MAC address).

Automatic Link-Local Address

You can verify the automatically generated Link-Local address with:

This allows each interface to have a unique IPv6 address without any manual configuration.
You can check them with the command:

R1# show ipv6 interface g0/1
GigabitEthernet0/1 is up, line protocol is up
  IPv6 is enabled, link-local address is FE80::A8BB:CCFF:FE12:3402
  Global unicast address(es):
    2001:41B1:1234:2:A8BB:CCFF:FE12:3402, subnet is 2001:41B1:1234:2::/64

Here you can see:

• The Link-Local address (FE80::)

• The Global Unicast address

Every IPv6 interface has a Link-Local address, even if no Global Unicast address is configured.

Manual Configuration of a Link-Local Address

In some scenarios, you may want to manually configure the Link-Local address instead of letting the router generate it automatically.