.. _multicast:

#########
Multicast
#########

VyOS facilitates IP Multicast by supporting **PIM Sparse Mode**,
**IGMP** and **IGMP-Proxy**.


************
PIM and IGMP
************

PIM (Protocol Independent Multicast) must be configured in every
interface of every participating router. Every router must also have the
location of the Rendevouz Point manually configured. Then,
unidirectional shared trees rooted at the Rendevouz Point will
automatically be built for multicast distribution. 

Traffic from multicast sources will go to the Rendezvous Point, and
receivers will pull it from a shared tree using IGMP (Internet Group
Management Protocol).

Multicast receivers will talk IGMP to their local router, so, besides
having PIM configured in every router, IGMP must also be configured in
any router where there could be a multicast receiver locally connected. 

VyOS supports both IGMP version 2 and version 3 (which allows
source-specific multicast).


Example
=======

In the following example we can see a basic multicast setup:

.. image:: /_static/images/multicast-basic.png
   :width: 90%
   :align: center
   :alt: Network Topology Diagram



**Router 1**

.. code-block:: none

   set interfaces ethernet eth2 address '172.16.0.2/24'
   set interfaces ethernet eth1 address '100.64.0.1/24'
   set protocols ospf area 0 network '172.16.0.0/24'
   set protocols ospf area 0 network '100.64.0.0/24'
   set protocols igmp interface eth1
   set protocols pim interface eth1
   set protocols pim interface eth2
   set protocols pim rp address 172.16.255.1 group '224.0.0.0/4'
   
**Router 3**

.. code-block:: none

   set interfaces dummy dum0 address '172.16.255.1/24'
   set interfaces ethernet eth0 address '172.16.0.1/24'
   set interfaces ethernet eth1 address '172.16.1.1/24'
   set protocols ospf area 0 network '172.16.0.0/24'
   set protocols ospf area 0 network '172.16.255.0/24'
   set protocols ospf area 0 network '172.16.1.0/24'
   set protocols pim interface dum0
   set protocols pim interface eth0
   set protocols pim interface eth1
   set protocols pim rp address 172.16.255.1 group '224.0.0.0/4'
   
**Router 2**

.. code-block:: none

   set interfaces ethernet eth1 address '10.0.0.1/24'
   set interfaces ethernet eth2 address '172.16.1.2/24'
   set protocols ospf area 0 network '10.0.0.0/24'
   set protocols ospf area 0 network '172.16.1.0/24'
   set protocols pim interface eth1
   set protocols pim interface eth2
   set protocols pim rp address 172.16.255.1 group '224.0.0.0/4'
   




Basic commands
==============

These are the commands for a basic setup.

.. cfgcmd:: set protocols pim interface <interface-name>

   Use this command to enable PIM in the selected interface so that it
   can communicate with PIM neighbors.


.. cfgcmd:: set protocols pim rp address <address> group <multicast-address/mask-bits>

   Use this comand to manually configure a Rendevouz Point for PIM so
   that join messages can be sent there. Set the Rendevouz Point address
   and the matching prefix of group ranges covered. These values must
   be shared with every router participating in the PIM network.
 

.. cfgcmd:: set protocols igmp interface eth1

   Use this command to configure an interface with IGMP so that PIM can
   receive IGMP reports and query on the selected interface. By defaul
   IGMP version 3 will be used.



Tuning commands
===============

You can also tune multicast with the following commands.

.. cfgcmd:: set protocols pim interface <interface> dr-priority <value>

   Use this PIM command in the selected interface to set the priority
   (1-4294967295) you want to influence in the election of a node to
   become the Designated Router for a LAN segment. The default priority
   is 1, set a  higher value to give the router more preference in the
   DR election process.


.. cfgcmd:: set protocols pim int <interface> hello <seconds>

   Use this command to configure the PIM hello interval in seconds
   (1-180) for the selected interface.


.. cfgcmd:: set protocols pim rp keep-alive-timer <seconds>

   Use this PIM command to modify the the time out value (31-60000
   seconds) for an `(S,G) <https://tools.ietf.org/html/rfc7761#section-4.1>`_
   flow. 31 seconds is chosen for a lower bound as some hardware
   platforms cannot see data flowing in better than 30 second chunks.


.. cfgcmd:: set protocols igmp interface <interface> join <multicast-address> source <IP-address>

   Use this command to allow the selected interface join a multicast
   group defining the multicast address you want to join and the source
   IP address too.


.. cfgcmd:: set protocols igmp interface <interface query-interval <seconds>

   Use this command to configure in the selected interface the IGMP
   host query interval (1-1800) in seconds that PIM will use.


.. cfgcmd:: set protocols igmp interface <interface query-max-response-time <deciseconds>

   Use this command to configure in the selected interface the IGMP
   query response timeout value (10-250) in deciseconds. If a report is
   not returned in the specified time, it will be asumed the `(S,G) or
   (*,G) state <https://tools.ietf.org/html/rfc7761#section-4.1>`_ has
   timed out.


.. cfgcmd:: set protocols igmp interface <interface> version <version-number> 

   Use this command to define in the selected interface whether you
   choose IGMP version 2 or 3. The default value is 3.



**********
IGMP Proxy
**********

:abbr:`IGMP (Internet Group Management Protocol)` proxy sends IGMP host messages
on behalf of a connected client. The configuration must define one, and only one
upstream interface, and one or more downstream interfaces.

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

.. cfgcmd:: set protocols igmp-proxy interface <interface> role <upstream | downstream>

   * **upstream:** The upstream network interface is the outgoing interface
     which is responsible for communicating to available multicast data sources.
     There can only be one upstream interface.

   * **downstream:** Downstream network interfaces are the distribution
     interfaces to the destination networks, where multicast clients can join
     groups and receive multicast data. One or more downstream interfaces must
     be configured.

.. cfgcmd:: set protocols igmp-proxy interface <interface> alt-subnet <network>

   Defines alternate sources for multicasting and IGMP data. The network address
   must be on the following format 'a.b.c.d/n'. By default the router will
   accept data from sources on the same network as configured on an interface.
   If the multicast source lies on a remote network, one must define from where
   traffic should be accepted.

   This is especially useful for the upstream interface, since the source for
   multicast traffic is often from a remote location.

   This option can be supplied multiple times.

.. cfgcmd:: set protocols igmp-proxy disable-quickleave

   Disables quickleave mode. In this mode the daemon will not send a Leave IGMP
   message upstream as soon as it receives a Leave message for any downstream
   interface. The daemon will not ask for Membership reports on the downstream
   interfaces, and if a report is received the group is not joined again
   upstream.

   If it's vital that the daemon should act exactly as a real multicast client
   on the upstream interface, this function should be enabled.

   Enabling this function increases the risk of bandwidth saturation.

.. cfgcmd:: set protocols igmp-proxy disable

   Disable this service.

Example
-------

Interface `eth1` LAN is behind NAT. In order to subscribe `10.0.0.0/23` subnet
multicast which is in `eth0` WAN we need to configure igmp-proxy.

.. code-block:: none

  set protocols igmp-proxy interface eth0 role upstream
  set protocols igmp-proxy interface eth0 alt-subnet 10.0.0.0/23
  set protocols igmp-proxy interface eth1 role downstream

Operation
=========

.. opcmd:: restart igmp-proxy

   Restart the IGMP proxy process.