MLD SSM Mapping

The MLD-SSM Mapping feature allows MLDv1 hosts to participate in SSM functionality, and eliminates the need for MLDv2. You can configure SSM map entries that specify the sources used for a group/group range for which SSM functionality is applied. You also have the option to configure domain name and DNS server to use to obtain the source list.

When a MLDV1 report is received, the configured sources are provided to PIM so that it can send source specific joins. When the host leaves, or when the membership times out, PIM is informed so that it can consider sending prunes.



The sources mapped to only the LPM group are used.

Feature Implementation Information

  • This feature is implemented as an extension to existing IGMP SSM support.
  • The CLI commands for this feature are applicable in VR context.
  • PIM is completely unaware of existence of this feature, so there is no change in PIM processing.
  • On last hop the (S, G) cache created through MLDv1 join is similar to the (S, G) cache created as a result of RPT to SPT switchover in PIM-SM. There is no indication that the cache is created as result of MLDv1 join, or MLDv2 report.


  • Only 50 sources (static or dynamic) are allowed for each group address, or group range.


    The DNS server may send only 14 IPv6 source addresses in its response thereby limiting the number of dynamic sources supported.
  • Only one DNS name is allowed for each group address/group range.