Layer 2 Multicast Traffic Control

CE.

The distribution of multicast traffic in a switched network can be controlled at Layer 2 using various protocols and processes. Out of the given options, the two protocols that can be used for this purpose are CGMP and IGMP snooping.

1. CGMP ( Cisco Group Management Protocol): It is a Cisco proprietary protocol used to control the forwarding of IP multicast traffic in a switched network. CGMP operates between a multicast router and a Layer 2 switch to dynamically manage the creation and deletion of Layer 2 multicast group memberships. When a multicast router receives a join or leave message from a host, it sends a CGMP message to the switch, which then updates its forwarding table accordingly. CGMP is typically used in conjunction with PIM Dense Mode.

2. IGMP Snooping: It is a Layer 2 multicast optimization technique that listens to IGMP messages between hosts and multicast routers to dynamically build a Layer 2 multicast forwarding table. The switch maintains a list of multicast group memberships for each port, and only forwards multicast traffic to ports that have requested to receive it. IGMP snooping is compatible with both IGMP v2 and IGMP v3 protocols, and can significantly reduce the amount of multicast traffic transmitted over the network.

In contrast, PIM (Protocol Independent Multicast) and IGMP (Internet Group Management Protocol) are Layer 3 multicast protocols. PIM is used to establish multicast distribution trees in a routed network, while IGMP is used by hosts to signal their interest in receiving multicast traffic. These protocols operate at Layer 3 and are not directly involved in controlling the distribution of multicast traffic at Layer 2.