PIM-SSM can create the MDTs using PIM Protocol. After the IMET route is received which identifies the core multicast group for the PIM joins to establish the MDT, PIM signals a join on the RPF path towards the route originator. This results in at least one MDT rooted at each VTEP node.
The number of MDTs is determined by the scope of the traffic inserted into the tree. It is not possible to create an MDT for each C-Multicast group as the number of such groups is virtually unbound. There are several options for creating MDTs:
In the PIM-SSM model, a leaf creates a P2MP tree rooted locally to send traffic to all participants. The number of MDTs in the fabric is bound by the number of leaf nodes/VTEPs.
Separate MDTs such as a Default MDT for flood or BUM traffic and a Data MDT for user multicast traffic can be created. However, a separate MDT just for flood traffic is not required as network congestion is negligible. IP Multicast fabric solution uses the same MDT for both types of traffic.