Cisco Group Management Protocol CGMP is primarily limited to forward IP multicast packets that only connect to the IP multicast client. These clients automatically add and leave the group that receives IP multicast traffic, and the switch changes its forwarding behavior based on the request. CGMP mainly provides the following services:
Allow IP multicast packets to be swapped to those ports with IP multicast clients. Save network bandwidth in the user field and not broadcast unnecessary IP multicast traffic. There is no need to change the terminal host system. No additional overhead is generated when you create a separate VLAN for each multicast group in the switched network.
Once CGMP is activated, it automatically identifies the port connected to the CGMP-Capable router. CGMP is activated by default, which supports up to 64 IP multicast group registration. Supporting the multicast router for CGMP periodically sends CGMP to join information (Join Messages) to advertise themselves to perform network exchange behaviors. Receive the switch saving information and sets a timer similar to the router hold time (HOLDTIME). For each of the Switches, the timer is also updated. When the router holds time termination, the switch is responsible for removing all the multicast groups known by the CGMP.
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