# MLD SSM Mapping Overview

Source-specific multicast (SSM) mapping enables the router to determine one or more source addresses for group G. The mapping effectively translates an Multicast Listener Discovery version 1 (MLDv1) multicast listener report to an MLDv2 report, enabling the router to continue as if it had initially received an MLDv2 report. After the router is joined to these groups, it sends out Protocol Independent Multicast (PIM) join messages and continues to enable joining from these groups, as long as it continues to receive MLDv1 membership reports and no change occurs to the SSM mapping for the group.

When you statically configure SSM mapping, the router can discover source addresses from a statically configured table.

The following applies when you configure SSM mapping:

- When enabled, and either you have not configured a static SSM map or the router cannot find any matching access lists, the router continues to accept (*,G) groups. The PIM SSM range must deny any unacceptable SSM group addresses.
- When you issue the no ipv6 mld ssm-map enable command, the router removes all SSM map (S,G) states and establishes a (*,G) state.
- You can enter multiple ipv6 mld ssm-map static commands for different access lists. Also, you can enter multiple ipv6 mld ssm-map static commands for the same access list, as long as the access list uses different source addresses.
- SSM maps do not process statically configured groups.

#### Related Documentation

- Configuring MLD SSM Mapping
- ipv6 mld ssm-map enable
- ipv6 mld ssm-map static