Multicast PIM-SM
Table of Contents
PIM-SM requires the following components: a Rendez-vous Point, shared trees, source trees.
PIM Register and Register Stop messages #
PIM register messages are sent by a PIM router to the Rendez-vous Point when it [the PIM router] receives multicast traffic from a streaming source.
PIM RP sends a PIM register stop message to signal to the PIM router that it [the RP] has received the PIM register message.
Incoming Interfaces vs Outgoing Interface List#
Incoming Interface#
The PIM router’s interface that receives – or is supposed to receive – multicast traffic from the multicast source.
Outgoing Interface List (OIL)#
The PIM router’s interface that received a request for multicast traffic, whether the request is an IGMP Join or PIM Join.
PIM Join and IGMP Join requests #
In PIM-SM, a multicast tree is not built unless a PIM router sends a PIM Join request to the PIM RP.
PIM Join request != IGMP Join request.
A PIM router sends a PIM Join request to the PIM RP only if it [the PIM router] has received a IGMP Join request from a client attached to it which is interested in the multicast traffic.
PIM Join requests are issued by PIM routers. The destination address is a multicast group address.
The RP is also eligible to send PIM Join requests.
The IGMP Join request concerns one specific multicast group, which is defined by the multicast group address.
IGMP Join requests are issued by multicast clients. The destination address is a multicast group address.
IGMP Join is aka IGMP Membership Report.
Mroutes#
A PIM router connected to a multicast source will receive multicast frames as soon as the source starts streaming. The PIM router will add mroutes in its multicast routing table.
Source of the tree in a shared tree != streaming source.
Source of the tree in a source tree == streaming source.
Mroutes expire shortly after the PIM router no longer receives frames destined to that multicast group.
For each multicast group, a PIM router installs a shared tree mroute rooted at the RP, and a source tree mroute rooted at the streaming source.
![[showipmroute239.1.2.3.png]]
The first mroute describes a shared tree. The second mroute describes a source tree.
Rendez-vous Point (RP)#
Static RP#
#TBC
Dynamic RP#
| PIM version | RP Type |
|---|---|
| PIM v1 | Auto-RP |
| PIM v2 | BootStrap Router (BSR) |
Flags#
#TBC
REGISTER, REGISTER STOP#
#TBC
Packet Flow Example#
https://eventhelix.com/networking/igmp/igmp-query-join-leave.pdf
PIM-SM Show Commands#
show ip pim neighbors show ip pim interface
#TBC