Cisco ENCOR Practice Exam 2026 – All-in-One Comprehensive Guide to Mastering Enterprise Network Core Technologies!

PIM Dense Mode (Protocol Independent Multicast Dense Mode) operates by flooding multicast traffic to all routers within a multicast domain initially. This approach assumes that users interested in receiving the multicast streams are present throughout the network, hence the term "dense mode." When a multicast sender sends data, it is sent to all of the routers on the network. Each router that receives the multicast traffic will then determine whether it needs the data based on whether any hosts in its local network segment have expressed interest in the multicast group by sending a join message.

If there are no interested receivers in a particular router's segment, that router will eventually stop forwarding the multicast traffic, sending a prune message back to the source, which reduces unnecessary traffic. However, the initial behavior of flooding the network with multicast packets until receivers prune away those they do not need is what characterizes PIM Dense Mode operation. This strategy is efficient in networks with many receivers because it ensures that multicast traffic reaches all devices before any pruning can occur.

In contrast, other modes or multicast processing approaches might handle traffic differently; for example, sparse mode would send traffic only to specific routers that have indicated interest in receiving the multicast streams, but that is not how Dense Mode functions.