If a Layer Two alter doesn't hit the capabilities to separate IGMP Snooping, it module be healthy to separate CGMP - Cisco Group Membership Protocol. CGMP allows the multicast router to impact with the Layer Two alter to decimate extra multicast forwarding.
CGMP module be enabled on both the multicast router and the switch, but the router's feat to do every the work. The router module be sending Join and Leave messages to the alter as needed. PIM staleness be streaming on the router programme covering the alter before sanctioning CGMP, as you crapper see:
R1(config)#int e0
R1(config-if)#ip cgmp
WARNING: CGMP requires PIM enabled on interface
R1(config-if)#ip pim sparse
R1(config-if)#ip cgmp
When CGMP is prototypal enabled on both the multicast router and switch, the router module beam a CGMP Join message, revelation the alter that a multicast router is today adjoining to it. This portion CGMP Join module include a Group Destination Address (GDA) of 0000.0000.0000 and the MAC come of the sending interface. The GDA is utilised to refer the multicast group, so when this is ordered to every zeroes, the alter knows this is an preceding CGMP Join, letting the alter undergo that the multicast router is online.
The alter makes an entry in its MAC plateau that this router crapper be institute soured the opening that the CGMP Join came in on. The router module beam a CGMP Join to the alter every time to help as a keepalive.
A workstation adjoining to the alter on opening 0/5 today wishes to tie multicast assemble 225.1.1.1. The Join communication is dispatched to the multicast router, but prototypal it module transfer finished the switch. The alter module do what you'd wait it to do - feature the maker MAC come and attain an entry for it in the MAC come plateau as existence soured opening alacritous 0/5 if there's not an entry already there. (Don't block that the MAC come plateau is also referred to as the CAM plateau or the bridging table.)
The router module then obtain the Join request, and beam a CGMP Join backwards to the switch. This CGMP Join module include both the multicast group's MAC come and the requesting host's MAC address. Now the alter knows most the multicast assemble 225.1.1.1 and that a member of that assemble is institute soured opening alacritous 0/5. In the future, when the alter receives frames sure for that multicast group, the alter module not batch the inclose as it would an uncharted multicast. Instead, the alter module nervy a double of the inclose to apiece opening that it knows leads to a member of the multicast group.
Two field benefits of CGMP are the definitive Join and Leave Group messages. In the incoming conception of this BCMSN communicating tutorial, well verify a countenance at the Leave Group messages.
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