Cisco Crosswork Planning Design 7.2.x User Guide

Source-Specific Multicast (SSM)

Updated: August 14, 2026

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Explains how source-specific multicast delivers packets from a specified source to receivers for improved efficiency and security.

A Source-Specific Multicast (SSM) is a multicast forwarding method that

delivers multicast packets to receivers only from a specified source address requested by the receiver
reduces resource requirements and improves security by restricting sources, and
is specified by an (S,G) parameter per multicast flow.

The (S,G) pair is labeled using a dot-decimal notation similar to IP addresses (for example, 1.1.1.1, 2.2.2.2). Each (S,G) pair is the name of a multicast flow, and each flow is listed in the Multicast flows table.

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