Module 12: IPv6 Addressing

Dual Stack

Allows IPv4 and IPv6 to coexist on the same network segment. These devices run both IPv4 and IPv6 protocol stacks simultaneously. Known as native IPv6, this means the customer network has an IPv6 connection to their ISP and is able to access content found on the internet over IPv6.

Tunneling

A method of transporting an IPv6 packet over an IPv4 network. The IPv6 packet is encapsulated inside an IPv4 packet, similar to other types of data.

Translation

Allows IPv6-enabled devices to communicate with IPv4-enabled devices using a translation technique similar to NAT for IPv4. An IPv6 packet is translated to an IPv4 packet and an IPv4 packet is translated to an IPv6 packet.

Here are four examples of ways to omit leading zeros:

01ab can be represented as 1ab

09f0 can be represented as 9f0

0a00 can be represented as a00

00ab can be represented as ab

As with IPv4, there are different types of IPv6 addresses. In fact, there are three broad categories of IPv6 addresses:

Unicast, Multicast, Anycast

Unicast

An IPv6 unicast address uniquely identifies an interface on an IPv6-enabled device.

Multicast

This address is used to send a single IPv6 packet to multiple destinations.

Anycast

This address is any IPv6 unicast address that can be assigned to multiple devices. A packet sent this address is routed to the nearest device having that address.

Unlike IPv4 devices that have only a single address, IPv6 addresses typically have two unicast addresses:

Global Unicast Address (GUA) and Link-local Address (LLA)

Global Unicast Address (GUA)

This is similar to a public IPv4 address. These are globally unique, internet-routable addresses. GUAs can be configured statically or assigned dynamically.

Link-local Address (LLA)

This is required for every IPv6-enabled device. LLAs are used to communicate with other devices on the same local link. With IPv6, the term link refers to a subnet. LLAs are confined to a single link. Their uniqueness must only be confirmed on that link because they are not routable beyond the link. In other words, routers will not forward packets with a link-local source or destination address.

There are two ways that a device can obtain an LLA:

Statically and Dynamically

There are two ways in which a device can obtain an IPv6 GUA automatically:

Stateless Address Autoconfiguration (SLAAC)

Stateful DHCPv6

The ICMPv6 RA message includes the following:

Network prefix and prefix length, Default gateway address, DNS addresses and domain name

Network prefix and prefix length

This tells the device which network it belongs to.

Default gateway address

This is an IPv6 LLA, the source IPv6 address of the RA message.

DNS addresses and domain name

These are the addresses of DNS servers and a domain name.

There are three methods for RA messages:

Method 1: SLAAC, Method 2: SLAAC with a stateless DHCPv6 server, Method 3: Stateful DHCPv6 (no SLAAC)

Method 1: SLAAC

"I have everything you need including the prefix, prefix length, and default gateway address."

Method 2: SLAAC with a stateless DHCPv6 server

"Here is my information but you need to get other information such as DNS addresses from a stateless DHCPv6 server."

Method 3: Stateful DHCPv6 (no SLAAC)

"I can give you your default gateway address. You need to ask a stateful DHCPv6 server for all your other information."

16-bit subnet ID

Creates up to 65,536 subnets.

64-bit interface ID

Supports up to 18 quintillion host IPv6 addresses per subnet (i.e., 18,000,000,000,000,000,000).