Setup Guide
PIM Sparse-Mode (PIM-SM)
Protocol-independent multicast sparse-mode (PIM-SM) is a multicast protocol that forwards multicast trac to a subnet only after a
request using a PIM Join message.
This behavior is the opposite of PIM-Dense mode, which forwards multicast trac to all subnets until a request to stop.
Topics:
• Implementation Information
• Protocol Overview
• Conguring PIM-SSM
• Enable PIM-SM
• Conguring S,G Expiry Timers
• Conguring a Static Rendezvous Point
• Conguring a Designated Router
• Electing an RP using the BSR Mechanism
• Creating Multicast Boundaries and Domains
• Enabling PIM-SM Graceful Restart
Implementation Information
The Dell Networking implementation of PIM-SM is based on IETF Internet Draft draft-ietf-pim-sm-v2-new-05.
• The maximum number of PIM interfaces is 95.
• The SPT-Threshold is zero, which means that the last-hop designated router (DR) joins the shortest path tree (SPT) to the source after
receiving the rst multicast packet.
• The Dell Networking OS reduces the number of control messages sent between multicast routers by bundling Join and Prune requests
in the same message.
• The system supports PIM-SM on physical, virtual local area network (VLAN), and port-channel interfaces.
• The system supports up to 128 PIM-source-specic multicast (SSM) neighbors/interfaces.
• IPv6 Multicast is not supported on synchronous optical network technologies (SONET) interfaces.
Protocol Overview
PIM-SM initially uses unidirectional shared trees to forward multicast trac; that is, all multicast trac must ow only from the rendezvous
point (RP) to the receivers.
After a receiver receives trac from the RP, PM-SM switches to SPT to forward multicast trac. Every multicast group has an RP and a
unidirectional shared tree (group-specic shared tree).
Requesting Multicast Trac
A host requesting multicast trac for a particular group sends an Internet group management protocol (IGMP) Join message to its
gateway router.
The gateway router is then responsible for joining the shared tree to the RP (RPT) so that the host can receive the requested trac.
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