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Webcast-Catalyst9k
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Multicast across Etherchannel

We have a customer who has their edge switch connected to two core switches, between the two core switches we have configured an Etherchannel. We have used Spanning Tree to block at the edge, therefore one core switch is the root for even vlans and the other is the root for odd vlans.

At the moment we have a multicast source connected to one core switch, the users that have this switch as their root do not have a problem, but the ones that have to go across the Etherchannel all complain bitterly about the quality of the Multicast Streaming. I believe this is to do with the fact that approximately 45 vlans are being trunked across this Etherchannel, so there is the potential of upto 45 copies of the same Multicast being sent across the Etherchannel. I know somebody has probably come across this problem before, but i've read a lot of literature about multicast but nothing goes into detail about the mechanics of Multicast traffic across an etherchannel.

We've now had to turn Multicasting off again because of the problems it created.

Please could somebody advise on the way forward to limit the amount of copies to be sent across the Etherchannel whilst using layer 2 between the core and the edge switch.

1 REPLY
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Re: Multicast across Etherchannel

Regarding multicasting even if a single host is present across a physical interface multicast packet has to be passed.So the best way is to prune the the Etherchannel interface so that multicast packet for un-necessary VLANs are filtered.For more info refer

http://www.cisco.com/en/US/products/hw/switches/ps708/products_tech_note09186a008059a9df.shtml#layer2.

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