IPv6

• The unicast link-local address is scoped and is used only between nodes connected on the same local link.
• When an IPv6 stack is enabled on a node, one link-local address is automatically assigned to each interface of the node at boot time.

The IPv6 link-local prefix FE80::/10 is used and the interface identifier in Extended Unique Identifier 64 (EUI-64) format is appended as the address's low-order 64-bit. Bits 11 through 64 are set to 0 (54-bit). Link-local addresses are only for local-link scope and must never be routed between subnets within a site

A site-local address is another unicast scoped address to be used only within a site. Site-local addresses are not enabled by default on nodes like link-local addresses, meaning that they must be assigned.A site-local address is similar to private address spaces in IPv4, such as 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16, as defined in RFC 1918,Address Allocation for Private Internets. Site-local addresses may be used by any organization that has not received aggregatable global unicast IPv6 spaces from a provider. A site-local prefix and address may be assigned to any nodes and routers within a site. However, site-local addresses must never be routed on the global IPv6 Internet.

the site-local address consists of the prefix FEC0::/10, a 54-bit field called Subnet-ID, and an interface identifier in EUI-64 format used as the low-order 64-bit

• Aggregatable global unicast addresses are IPv6 addresses used for the generic IPv6 traffic on the IPv6 Internet.
• Aggregatable global unicast addresses are similar to the unicast addresses used to communicate across the IPv4 Internet.
• Aggregatable global unicast addresses represent the most important part of the IPv6 addressing architecture.
• The structure of aggregatable global unicast enables a strict aggregation of routing prefixes to limit the size of the global Internet routing table.

Each aggregatable global unicast IPv6 address has three parts:

Prefix received from a provider— The prefix assigned to an organization (leaf site) by a provider should be at least a /48 prefix, as recommended in RFC 3177, IAB/IESG Recommendations on IPv6 Address Allocations to Sites. The /48 prefix represents the high-order 48-bit of the network prefix. Moreover, the prefix assigned to the organization is part of the provider's prefix.

Site— With one /48 prefix allocated to an organization by a provider, it is possible for that organization to enable up to 65,535 subnets (assignment of 64-bit's prefix to subnets). The organization can use bits 49 to 64 (16-bit) of the prefix received for subnetting.

Host— The host part uses each node's interface identifier. This part of the IPv6 address, which represents the address's low-order 64-bit, is called the interface ID.

IPv4-compatible IPv6 address— Used to establish an automatic tunnel to carry IPv6 packets over IPv4 networks. This address is related to a transition mechanism of the IPv6 protocol.

IPv4-mapped IPv6 address— Used only on the local scope of nodes having both IPv4 and IPv6 stacks. Nodes use IPv4-mapped IPv6 addresses internally only. These addresses are never known outside the node itself and should not go on the wire as IPv6 addresses.

The multicast address in IPv6 is defined by the IPv6 prefix FF00::/8

In IPv4, the time-to-live (TTL) is used to scope multicast traffic. IPv6 multicast has no TTL, because the scoping is defined within the multicast address.

• A multicast IPv6 address within the multicast scope that is automatically enabled on the interface for each unicast and anycast address assigned. Solicited-node multicast addresses are used in IPv6 to replace ARP and in duplicate address detection. Solicited-node multicast addresses in IPv6 are based on the prefix FF02::1:FF00:0000/104.

anycast is used for one-to-nearest communication. Anycast is a mechanism that delivers a packet sent to an anycast address of the nearest node member of the anycast group. Anycast enables a type of discovery mechanism to the nearest point. The network itself plays the key role in anycast by routing the packet to the nearest destination by measuring network distance

DAD and NDP are described in detail in Chapter 3.