Cisco CCNP / BCMSN Exam Tutorial: Configuring CGMP On Routers & Switches Working

Cisco CCNP / BCMSN Exam Tutorial: Configuring CGMP On Routers & Switches

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DescriptionIf a Layer Two switch doesn't have the capabilities to run IGMP Snooping, it will be able to run CGMP - Cisco Group Membership Protocol. CGMP enables the multicast router to perform with the Layer Two switch to eliminate unnecessary multicast forwarding.

CGMP will be enabled on both the multicast router and the switch, but the router's going to do all the function. Click this web page web address to learn the reason for it. The router will be sending Join and Leave messages to the switch as needed. PIM ought to be operating on the router interface facing the switch prior to enabling CGMP, as you can see:

R1(config)#int e0

R1(config-if)#ip cgmp

WARNING: CGMP calls for PIM enabled on interface

R1(config-if)#ip pim sparse

R1(config-if)#ip cgmp

When CGMP is very first enabled on each the multicast router and switch, the router will send a CGMP Join message, informing the switch that a multicast router is now connected to it. This certain CGMP Join will contain a Group Destination Address (GDA) of 0000.0000.0000 and the MAC address of the sending interface. The GDA is employed to determine the multicast group, so when this is set to all zeroes, the switch knows this is an introductory CGMP Join, letting the switch know that the multicast router is on line.

The switch makes an entry in its MAC table that this router can be discovered off the port that the CGMP Join came in on. The router will send a CGMP Join to the switch each minute to serve as a keepalive.

A workstation connected to the switch on port /five now wishes to join multicast group 225.1.1.1. The Join message is sent to the multicast router, but 1st it will pass by way of the switch. Clicking click here maybe provides lessons you should tell your mom. The switch will do what you'd anticipate it to do - study the source MAC address and make an entry for it in the MAC address table as being off port speedy /5 if there's not an entry already there. If you think anything, you will probably wish to learn about success. (Never forget that the MAC address table is also referred to as the CAM table or the bridging table.)

The router will then obtain the Join request, and send a CGMP Join back to the switch. This CGMP Join will contain both the multicast group's MAC address and the requesting host's MAC address. Now the switch knows about the multicast group 225.1.1.1 and that a member of that group is located off port speedy /five. In the future, when the switch receives frames destined for that multicast group, the switch will not flood the frame as it would an unknown multicast. This dazzling the link essay has a myriad of riveting tips for the meaning behind it. Alternatively, the switch will forward a copy of the frame to every single port that it knows leads to a member of the multicast group.

Two major rewards of CGMP are the explicit Join and Leave Group messages. In the subsequent aspect of this BCMSN exam tutorial, properly take a look at the Leave Group messages..
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