3.2. Network part, also known as prefix

3.2.3.1. 6bone test addresses

These were the first global addresses which were defined and in use. They all start with

3ffe:

Example:

3ffe:ffff:100:f102::1

A special 6bone test address which will be never be globally unique begins with

3ffe:ffff: 

and is mostly shown in examples, because if real addresses are shown, its possible for someone to do a copy & paste to their configuration files. Thus inadvertently causing duplicates on a globally unique address. This would cause serious problems for the original host (e.g. getting answer packets for request that were never sent). You can still apply for one of these prefixes, see here How to join 6bone. Also some tunnel brokers still distribute 6bone test address prefixes.

3.2.3.2. 6to4 addresses

These addresses, designed for a special tunneling mechanism [RFC 3056 / Connection of IPv6 Domains via IPv4 Clouds and RFC 2893 / Transition Mechanisms for IPv6 Hosts and Routers], encode a given IPv4 address and a possible subnet and begin with

2002:

For example, representing 192.168.1.1/5:

2002:c0a8:0101:5::1

A small shell command line can help you generating such address out of a given IPv4 one:

ipv4="1.2.3.4"; sla="5"; printf "2002:%02x%02x:%02x%02x:%04x::1" `echo $ipv4
╛ | tr "." " "` $sla

See also tunneling using 6to4 and information about 6to4 relay routers.

3.2.3.3. Assigned by provider for hierarchical routing

These addresses are delegated to Internet service providers (ISP) and begin with

2001:

Prefixes to major (backbone owning) ISPs are delegated by local registries and currently they assign to them a prefix with length 35.

Major ISPs normally delegate to minor ISPs a prefix with length 48.

3.2.4.1. Multicast scopes

Multicast scope is a parameter to specify the maximum distance a multicast packet can travel from the sending entity.

Currently, the following regions (scopes) are defined:

• ffx1: node-local, packets never leave the node.

• ffx2: link-local, packets are never forwarded by routers, so they never leave the specified link.

• ffx5: site-local, packets never leave the site.

• ffx8: organization-local, packets never leave the organization (not so easy to implement, must be covered by routing protocol).

• ffxe: global scope.

• others are reserved

3.2.4.2. Multicast types

There are many types already defined/reserved (see RFC 2373 / IP Version 6 Addressing Architecture for details). Some examples are:

• All Nodes Address: ID = 1h, addresses all hosts on the local node (ff01:0:0:0:0:0:0:1) or the connected link (ff02:0:0:0:0:0:0:1).

• All Routers Address: ID = 2h, addresses all routers on the local node (ff01:0:0:0:0:0:0:2), on the connected link (ff02:0:0:0:0:0:0:2), or on the local site (ff05:0:0:0:0:0:0:2)

3.2.4.3. Solicited node link-local multicast address

Special multicast address used as destination address in neighborhood discovery, because unlike in IPv4, ARP no longer exists in IPv6.

An example of this address looks like

ff02::1:ff00:1234

Used prefix shows that this is a link-local multicast address. The suffix is generated from the destination address. In this example, a packet should be sent to address "fe80::1234", but the network stack doesn't know the current layer 2 MAC address. It replaces the upper 104 bits with "ff02:0:0:0:0:1:ff00::/104" and leaves the lower 24 bits untouched. This address is now used `on-link' to find the corresponding node which has to send a reply containing its layer 2 MAC address.

3.2.5.1. Subnet-router anycast address

A simple example for an anycast address is the subnet-router anycast address. Assuming that a node has the following global assigned IPv6 address:

3ffe:ffff:100:f101:210:a4ff:fee3:9566/64  <- Node's address

The subnet-router anycast address will be created blanking the suffix (least significant 64 bits) completely:

3ffe:ffff:100:f101::/64  <- subnet-router anycast address