====
IPv6
====

.. sidebar:: Contents

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IPv6 is the most recent version of the Internet Protocol (IP). It was first
described in RFC#2460, Internet Protocol, Version 6 (IPv6) Specification. IPv6
was proposed when it became clear that IPv4's 32-bit addressing scheme was
inadequate to meet the demands of Internet growth. It is based on the Internet
Protocol, but with far more address space (from 32 bits to 128 bits).

Unnecessary fields have also been eliminated in order to simplify the header and
thus reduce processing time. Although the address size is 128 bits, the IPv6
header size is only 40 bytes. All additional fields are organized in the
extension headers.

IPv6 architecture can coexist with that of IPv4 users, thus easing migration to
IPv6 while providing improvements to security, quality of service and globally
unique IP addresses. IPv6 offers greater address space and allows networks to
scale and provide global reachability. The flexibility of IPv6 addresses reduces
the need for private addresses and the use of Network Address Translation (NAT).
In addition, IPv6 enables new application protocols that do not require special
processing by border routers sitting at the edge of the network.


Configuration
=============

By default, IPv6 is enabled on OSDx devices and all interfaces function as
*router interfaces*. This can be changed using the ``disable-forwarding``
command:

.. code-block:: none

  set interfaces <kind> <name> ipv6 disable-forwarding

That command forces the interface to behave as a host (it inhibits the routing
of packets through this interface).

This can be globally changed by using the following command:

.. code-block:: none

  set system ipv6 disable-forwarding


All interfaces working in *router* mode automatically announce RAs (Router
Advertisements). This can be disabled by using the following configuration
command:

.. code-block:: none

  set interfaces <kind> <name> ipv6 router-advert disable

.. note::

    That command can not be configured if ``disable-forwarding`` is enabled for
    that interface.


IPv6 addresses can be generated using three fundamental mechanisms:

* Manual.
* Stateless.
* Stateful.

The stateful and stateless configurations provide autoconfiguration address
mechanisms.


Manual address configuration
----------------------------

Manual configuration offers several possibilities. The most basic one is to
assign an absolute address to the interface. This can be achieved by using
the following configuration command:

.. code-block:: none

  set interfaces <kind> <name> address <ipv6 address>


*Example*:

.. code-block:: none

  set interfaces ethernet eth0 address '2001:db8:100:f101::1/64'


Addresses can also be configured by using the Extensible Unique Identifier-64
(EUI-64) method:

.. code-block:: none

  set interfaces <kind> <name> ipv6 address eui64 <ipv6 prefix>


*Example*:

.. code-block:: none

  set interfaces ethernet eth0 ipv6 address eui64 '2001:db8:100:f101::/64'


.. warning::

    This method automatically generates an IP address using the interface's MAC
    and it is now not recommended for privacy reasons.



Stateless address configuration
-------------------------------

Stateless autoconfiguration is based on the SLAAC (Stateless Address
Autoconfiguration) procedure, whose fundamental idea is to form an address from
a 64-bit prefix (announced in an RA message) and a suffix generated in the host
itself.

This can be enabled by using the following configuration command:

.. code-block:: none

  set interfaces <kind> <name> ipv6 address autoconf

.. note::

    ``disable-forwarding`` needs to be configured in that interface for this
    command to work.



Stateful address configuration
------------------------------

Stateful autoconfiguration is achieved by means of the DHCPv6 protocol.

A DHCPv6 client can be started by using the following configuration command:

.. note::

  According to RFC#8415, addresses obtained through DHCPv6 have a 128 bits
  prefix length.


Monitoring
==========

Most common operational commands have built-in support for IPv6.

*Examples:*

* :osdx:op:`ping *`.
* :osdx:op:`traceroute *`.
* :osdx:op:`nslookup *`.
* :osdx:op:`telnet *`.
* :osdx:op:`ssh *`.

Command :osdx:op:`monitor router-advertisement` is specific for IPv6 and can be
used for RA debugging purposes.


Examples
========

There is a plethora of examples with IPv6 described at the
:ref:`examples section <intro-examples>`.

:ref:`Here <example_interfaces_ethernet_ipv6_address>`, you can find some basic
examples related to *IPv6 address assignation*.

:ref:`This entry <example_interfaces_ethernet_ipv6_router-advert_router-advert>`
includes examples to configure and debug RA.