Version 4.1 - 1.7 IP Multicast
I have to admit that in R/S, Multicast was never a favorite topic of mine. I understood it, but it was just one of those subjects that you didn't deal with often (at least not directly). And when you did, it was dry. But it's listed as a topic, so I'm going to push on through it.
Let's start with Multicast Addressing. The multicast address space is the "Class D" address space. All multicast addresses fall in the range of 224.0.0.0 to 239.255.255.255.
The Cisco guide for Configuring Multicast Routing is extensive. Again, we need to remember the exam scope and not get too into the weeds on this. I don't think they will focus on every detail of Multicasting - just the points that you would need to know relating to security implementations.
So the most important thing in the guide would be the Basic and Advanced Configuration Task Lists. Some of the topics will be covered in greater detail in the 1.7 sub-topics, but look at the required and optional tasks. You probably won't be required to know how to configure Auto-RP, but you should know what it is and when/where you configure it. If you see a topic in that list that you don't recognize, read it. Understand what the terms mean so that if you see them - you can determine if it's relevant to the question or a distractor.
Remember that the purpose of multicast is to be able to send one packet that gets to a group. It is used with video to conserve bandwidth. The source sends one packet to the group and it gets forwarded to the hosts that have joined the group. It is also used in routing protocols - where update messages are sent to the 224.0.0.5 address (OSPF example).
Multicast-capable routers can create two kinds of distribution trees. The first kind is a source tree - with the source of the traffic as the "root" of the tree. This is also called SPT - Shortest Path Tree. The other kind of tree is a shared tree. These use a Rendezvous Point (RP) as the root of the tree. Multicast also uses a method to forward the packet away from the source (rather than towards the receiver) - which is known as Reverse Path Forwarding. The uRPF check makes sure that the distribution tree is loop-free.
That's about all I want to cover in general about Multicasting in general. The subtopics will explore more about specific areas of multicasting.