Objectives
The simulator ticks each one as soon as the network meets it.
On every router configure ip pim ssm default (232.0.0.0/8).
On R3 set ip igmp version 3 on GigabitEthernet0/1, PC3’s LAN.
On PC3 join 232.1.1.1 from source 10.1.1.10.
From SRC ping 232.1.1.1: PC3 replies.
On R3, show ip mroute: only an (S,G) entry, flagged s (SSM), and no (*,G).
Before you start
An SSM channel is a (source, group) pair. IGMPv2 can only say “I want this group”, so a source-specific join needs IGMPv3 on the receiver LAN. Routers ignore (*,G) joins in the SSM range, which is why SSM needs no RP and has no shared tree.
Concept
Source-specific multicast (SSM)
With SSM the receiver names the source as well as the group, so its router can join the source straight away. There is no RP, no register and no shared tree; a channel is simply (S,G). The SSM range is 232.0.0.0/8.
Concept
IGMP: how a receiver asks for a group
A multicast group (224.0.0.0/4) is an address many receivers can listen to at once. A host tells its local router it wants a group with an IGMP membership report; the router then pulls the stream toward that LAN. IGMPv2 can only name the group; IGMPv3 can also name the source.
