IPv6
====


Basics
------

Global Unicast Address:
    * Globally unique and routable
    * Equivalent to Public IPv4 Address
    * Begins with hex 2 or 3
    * can be source or destination
    * Is not a mandatory address
    * example ``2001:db8:cafe:1::100``


Link-Local Unicast Address:
    * Local to a logical network subnet (connected to one ethernet interface)
    * Not routable beyond the local subnet
    * Every Device must have a link local per network interface based on its MAC address
    * begin with ``fe80::``


Unspecified Address:
    * all zeros ``[::]`` which is equivalent to IPv4 ``0.0.0.0``
    * Can only be set as a source address
    * Can be used by a process to bind to all interfaces
    * Can be used during Neighbour Discovery before setting up a Unicast Address
    * Is never routed / forwarded by a router


Solicited-Node Multicast Address
    * Similar to IPv4 Broadcast Address: ``192.168.0.0\24`` broadcast ``192.168.0.255``
    * Used by ICMPv6 NDP (Neighbour Discovery Protocol) to determine the MAC address of a host on a local Network
    * Only Valid as a destination Address, and never routed off the link or the subnet
    * Starts with ``ff02::1:ff00:0/104``



Interface ID of a Node or Device
    Equivalent to the host Portion of IPv4. A Node or a Device can have multiple Interfaces, and A
    Single Interface can have Multiple IPv6 addresses


Prefix and Prefix Length
    A prefix Is the network Portion of an IPv6 address, size is from /0 to /128
    If the Prefix Length is /64 then the Interface ID length is /64
    If the Prefix Length is /70 then the interface ID Length is /48




Neighbour Discovery Protocol (NDP) Over ICMPv6
-----------------------------------------------

NDP is used for on-link (same subnet) device discovery and messaging

Includes 5 Message types

* Router Solicitation (RS)
* Router Advertisement (RA)
* Neighbour Solicitation (NS)
* Neighbour Advertisement (NA)
* Redirect Message


Dynamic Address Allocation
***************************

Stateless Address Autoconfiguration (SLAAC)
    * Uses all the information in the RA for its addressing needs
    * RA includes Prefix Length and Prefix, and used to create a global Unicast Address
    * The device will use the Source IPv6 Address in the RA as its default gateway

SLAAC + Stateless DHCPv6
    * Similar to SLAAC
    * The device obtains the default Gateway from the RA
    * Addtionally the RA Suggests to the device to contact a DHCPv6 Server for Extra Information
    * Extra info includes DNS Server, among other info
    * Stateless DHCPv6 does not provide nor maintain a table of Unicast Addresses

Stateful DHCPv6
    * the RA Suggests to the device to obtain all IPv6 Addressing info from a Stateful DHCPv6 server
    * The Device obtains the default gateway from the RA
    * The device obtains A global Unicast Address, and DNS Servers from the Stateful DHCPv6 Server
    * Similar to DHCPv4