Question

what is the role of routing table in multicast ?

Answer 1

A routing table is a set of rules, often viewed in table format, that is used to determine where data packets traveling over an Internet Protocol (IP) network will be directed. All IP-enabled devices, including routers and switches, use routing tables.

In Multicast Routing the objectives are

1. Every member should receive only one copy
2. Non members should not receive a copy
3. There should be no loops
4. The Distance between source and destination should be shortest 

All these objectives can be achieved only by creating routing tables