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Routing & Switching · Intermediate

Source-Specific Multicast (SSM)

A PIM mode in which receivers join a specific (S,G) channel directly, eliminating the RP and shared tree.

Definition

SSM uses the 232.0.0.0/8 range by default and requires IGMPv3 or MLDv2 so receivers can specify the source. It is simpler and more secure than ASM because only the requested source is delivered.

Example

ip pim ssm default

Exam tip

SSM needs IGMPv3; no RP, Auto-RP, BSR or MSDP is required.

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