IPv6 Address Categories
All IPv6 addresses fall into one of three categories
Unicast -
Unicast addresses identify a unique interface on an IPv6 device.
It is a one to one connection between a source and destination.
Examples of IPv6 Unicast addresses include:
Global Unicast -
Similar to a public IPv4 address
Can be used as a public address on the internet
Globally unique
Can be static or dynamic
Link-Local -
Only used on a local network link to uniquely identify a
host Not routable on the public internet
No router will forward a link-local address
Every IPv6 enabled networked device is required to have a link-local address
Multiple interfaces on the same device can have the same link-local address
Loopback - (::1/128)
Used by a host to ping itself to test the TCP/IP
stack It cannot be assigned to a physical interface
Unspecified Address - (::/128)
Is only used as a source address to indicate the absence of an actual address
Unique Local -
Unique local addresses are roughly the same as IPv4 private addresses
Embedded IPv4 -
Used to transition IPv4 networks into IPv6
Multicast -
Multicast addresses are used to send a single packet to multiple destinations simultaneously.
Anycast -
Anycast addresses are described as a one-to -nearest or one -to-one-of -many packet
delivery. For example, all routers in the same network will be assigned the same Anycast
address. A packet sent to that address will only be delivered to the closest router with that
address based on routing protocol metrics. Anycast addresses can be pulled from Global
Unicast, Site-Local, or Link-Local address ranges. The first address and the last 128
addresses in a /64 Global Unicast range are reserved as the Subnet-Router Anycast
Address.
There are no broadcast addresses in IPv6. 11
Global Unicast IPv6 Address
128 bits
64 bits 64 bits
48 bits 16 bits
Global Routing Prefix Subnet ID Interface ID
The first 3 bits will be 001 for a Global Unicast address.
The first hextet determines the type of address.
Global Routing Prefix -
This is assigned by the ISP to a customer or site.
The Global Routing Prefix is determined by the prefix-length notation. (example /48 or /64).
This is similar to the network portion of an IPv4 address.
Subnet ID -
This is similar to the subnet portion of an IPv4 address.
The difference is in IPv4 the subnet is borrowed from the host portion of the address.
In IPv6 the Subnet ID is a separate field (/48 to /64) and not necessarily part of the Interface ID.
Interface ID -
The Interface ID uniquely identifies a interface on the local subnet.
Subnet Prefix
The Subnet Prefix is the address space used by the Global Routing Prefix and the Subnet
ID, and can range from 0 to 128. The preferred Subnet Prefix length is /48 to /64 for
customers or sites.
Global Routing Prefix Subnet ID Interface ID
Subnet Prefix /64
RFC 4291 recommends that the Interface-ID or host portion of your IPv6 address be 64 bits.
