When SSM source and group filtering is enabled, then for groups in the SSM space the local router will - process PIM (S,G) Join messages received on this interface only if the {source, group} pair is included in the extended access list corresponding to the list index value configured for this object - only send PIM (S,G) Join messages over this interface if the {source, group} pair is included in the extended access list corresponding to the list index value configured for this object. In other words, the extended access list is a whitelist of the SSM {source, group} pairs for which DC-PIM is permitted to request or receive traffic over the interface. rlPimInterfaceSsmSrcAndGrpFilter defaults to an empty string, which indicates that no access list is specified. If the name does not correspond to a valid access list, no {source, group} pairs will match the list and therefore all PIM (S,G) Join messages will be filtered.