Reference Guide

PIM Sparse-Mode (PIM-SM) | 683

PIM Sparse-Mode (PIM-SM)

PIM Sparse-Mode (PIM-SM) is supported on the S5000 switch.

PIM-Sparse Mode (PIM-SM) is a multicast protocol that forwards multicast traffic to a subnet only upon

request using a PIM Join message; this behavior is the opposite of PIM-Dense Mode, which forwards

multicast traffic to all subnets until a request to stop.

This chapter includes the following topics:

• Implementation Information

• Protocol Overview

• Configuring PIM-SM

• Enabling PIM-SM

• Configuring S,G Expiry Timers

• Configuring a Static Rendezvous Point

• Configuring a Designated Router

• Creating Multicast Boundaries and Domains

Implementation Information

• The Dell Networking implementation of PIM-SM is based on the IETF Internet Draft

draft-ietf-pim-sm-v2-new-05.

• The S5000 supports a maximum of 31 PIM interfaces and 2K multicast entries including (*,G), and

(S,G) entries. There is no limit on the number of PIM neighbors the S5000 can have.

• The SPT-Threshold is zero, which means that the last-hop designated router (DR) joins the shortest

path tree (SPT) to the source upon receiving the first multicast packet.

• Dell reduces the number of control messages sent between multicast routers by bundling Join and

Prune requests in the same message.

• Dell Networking OS supports PIM-SM on physical, VLAN, and port-channel interfaces.

Protocol Overview

PIM-SM initially uses unidirectional shared trees to forward multicast traffic; that is, all multicast traffic

must flow only from the Rendezvous Point (RP) to the receivers. Once a receiver receives traffic from the

RP, PM-SM switches to shortest path trees (SPT) to forward multicast traffic. Every multicast group has an

RP and a unidirectional shared tree (group-specific shared tree).