Unanswered Question
Jun 8th, 2008

Multicast feed when delivered to trunk interface is it going to have multiple copies of the same traffic.I mean bandwidth will be multiplied based on number of vlans.

I have this problem too.
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n.nandrekar Sun, 06/08/2008 - 21:38

Nop! This will not be the case. It will depend on the IGMP membership recieved and vlan associated with it.

If igmp membership is recieved on say all 500 vlans configured on the trunk, the traffic will be replicated for all the 500 vlans.

Hope I amswered your question. If I have mis-interpreted it, please elaborate on the scenario.



tahseen12 Sun, 06/08/2008 - 21:54

Thnks for reply but you are saying the same that bandwidth will be replicated on trunk interface since multiple copies will be used to sent to each vlan.Thats what i said.

So if multicast feed is of 100 Mb and I have 3 vlans on trunk it will become 300Mb right?so interface traffic will increase by 3 times for example.

n.nandrekar Sun, 06/08/2008 - 22:11

yes! Thats correct. But this is true if you have multicast recievers on all the 3 vlans and if all the 3 vlans recieve Igmp membership reports. If there are 5 vlans on the trunk, and only 1 vlans as a pc that requires multicast stream, then the multicast stream will be sent on only that vlan and not replicated. So the bandwidth consumed will not multiply. But if u have recievers on all the 5 vlans, it will be multiplied when the traffic is sent out on the link.

Hope this answers your question. ( Please rate the post in case it does.)




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