Source-Specific Multicast
Source-specific PIM is acquired from PIM dispersed mode. It is added able than dispersed mode. In
sparse mode, a PIM Join bulletin from a host after-effects in sending cartage from all multicast sources
toward that receiver. SSM instead uses the (S,G) archetypal from the alpha to bear multicast traffic
to a accurate accumulation affiliate from alone one source, which the abutting host specifies, rather than
from all multicast senders for that group. SSM requires MLDv2 to operate, because MLDv1
messages do not accommodate the appropriate advice to abutment SSM. However, SSM mapping
supports MLDv1 hosts by either DNS or changeless hostname-to-IPv6 abode mappings. This allows
routers to attending up the antecedent of a multicast beck back they accept an MLDv1 Join message.
This affection permits extending SSM to MLDv1 hosts, in befitting with SSM’s abstraction of
maximizing multicasting efficiency.
SSM mapping charge be enabled globally on a router by application the ipv6 mld ssm-map enable
command. SSM mapping uses DNS by default. Disable DNS lookup for SSM mapping by using
the no ipv6 mld ssm-map concern dns command. Specify changeless mappings by application the ipv6 mld
ssm-map changeless access-list-name source-address command.