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IPv6 – Part 3 (Address Types in IPv6)

There are three main address types in IPv6. These are:

• Unicast Addresses
• Multicast Addresses
• Anycast Addresses

As you can see, in IPv6 there is no broadcast address type. But here,with IPv6, an additional address type, anycast addresses are coming. Here, the unicast address type has also its sub address types. These Unicast

Address types are:

o Aggregatable Global Address
o Unique Local Address
o Link-Local Address
o IPv4-Compatible IPv6 Address

To sum up, our address hierarchy will be like below:

• Unicast Addresses
   o Aggregate Global address
   o Unique Local Address
   o Link-Local Address
   o IPv4-Compatible IPv6 Address

• Multicast Addresses
• Anycast Addresses

Beside these addresses, there is one more address type. This address type is reserved addresses.

Let’s check all these address types deeply.

Reserved Addresses

These addresses are start with “0000 0000” first 8 bits. Its prefix is 0::/8 .

For example:

0:0:0:0:0:0:0:0 Unspecified Address
0:0:0:0:0:0:0:1 Loopback Address

Unicast Addresses

Aggregate Global Addresses

These addresses are mandatory for global connection. Aggregatable global addresses are used on links that are aggregated upward through organizations, and eventually to the ISPs.

If we go more deeply, we can use the below shape to understand an aggregate global address.

Here are some definitions that will help us to understand aggregate global addresses.

TLA : Top-level Aggregation Identifier. High level registries like RIPE assigned ranges of TLAs.
NLA : Next-level Aggregation Identifier. Produced by subdivision of TLAs and assigned from high level registries like RIPE to lower-tiered ISPs . ISPs allocate these to their customers.
SLA : Site-level Aggregation Identifier. Used by customers to subdivide the address space to local networks.

Unique Local Addresses

These address is a globally unique address and intended for the lcoal communication. These addresses are not routable on the internet, they only routable on a limited area, such as a site.

Link-Local Addresses

These address is also a unicast address like the above two address. This adress can be automatically configurad and do not need to be globally unique. During automatic configuration, the interface can be assigned an link-local address with a EUI-64 format.

Link-Local addresses are used in the neighbor dicovery and stateless autoconfiguration.

IPv4-Compatible IPv6 Addresses

This IPv4-compatible IPv6 addresses are IPv6 unicast addresses that has zeros in the high-order 96 bits and an IPv4 address in the low-order 32 bits of the address. The full address is used as IPv6 address and the low-order 32 bits is used as IPv4 address.

Anycast Addresses

Anycast addresses are the addresses that has come with IPv6. This address is assigned to a set of interfaces that typically belong to the different nodes. Then, when a packet send to the anycast address, it is delivered to the closest interface.

Multicast Addresses

Anycast addresses are the IPv6 addresses that has a prefix of FF00::./8. A packet that sent to a multicast address, is delivered by the interfaces identifeed by that multicast address.

The first octet are full of 1(1111 1111). And the second octet is consist of lifetime and scope values. The lifetime is “0” then the multicast address is permanent, if it is “1”, then the multicast address is temporary. And the scope part indicates that if the multicast address is in which scope, a node, a link, a site or an organization.

We can give some examples to the multicast addresses. For example:

FF01::1 All nodes (node)
FF01::2 All Routers (node)
FF02::2 All Routers (link)

Beside these addresses, there is one more address type that will not use anymore. This is “Site-local addresses”. Because the RFC 3879 deprecates the use of Site-local addresses.

I hope this article will be usefull for you;) keep on ipcisco.com.

You can find the other IPv6 articles below…

IPv6 – Part 1 (IPv6 and IPv6 Addresses)
IPv6 – Part 2 (What does IPv6 bring?)
IPv6 – Part 3 (Address Types in IPv6)
IPv6 – Part 4 (Subnetting IPv6)

IPv6 Static Route Configuration Examples…

IPv6 Static Route Configuration on Cisco
IPv6 Static Route Configuration on Juniper

IPv6 Routing Protocols…

IPv6 Routing Protocols – Part 1
IPv6 Routing Protocols – Part 2 (OSPFv3)

IPv4 and IPv6 Headers…

IPv4 and IPv6 Headers

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About the Author
Gokhan Kosem is a telecommunation and network engineer. His ambition to IP networks and end-to-end system installation made him to prepare this web-site. By sharing his experiences about various networking protocols beside different system installation experiences and Cisco, Juniper, Alcatel-Lucent devices configurations, he is aimed to be helpful for his collegues in all over the world. He is currently lives in Istanbul, Turkey.

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