multicast rate limiting

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Sep 24th, 2007
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We have Multicast running in our sites .Some times due to huge multicast traffic we have seen that the cpu shoots up to 95 % and we end up killing or shuttig down multicast.

My questions is is there a way by which we can rate limit the multicast traffic that is origination from a particular VLAN. If so how can we do that .I have heard of rate limiting based on multicast group..But Iam looking ofr based on VLAN. If there is way can you suggest some ways and sample config


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IanTarasevitsch1995 Mon, 09/24/2007 - 23:42
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You can rate-limit the individual physical interfaces with the "storm-control multicast" command, but I do not think you can apply that to a SVI for a VLAN. You may want to look at which interfaces are sourcing the heavy traffic and storm-control those interfaces.



athambi Tue, 09/25/2007 - 00:04
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I guess in 6500 we have an option to rate limit based on layer 3 vlan.Atleast I see that option in the configuration.Please

refer the attachment .

If I issue the command

distrib-f1.lab(config-if)#ip multicast rate-limit in 4500

does it have effect on incoming or outgoing traffic

IanTarasevitsch1995 Tue, 09/25/2007 - 00:22
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Since you use "ip multicast rate-limit IN" it should impact your inbound/ingress side of the interface. You may want to see if you can limit packets per second (pps) since that will normally have a much bigger impact on router performance than actual bandwidth being passed.



athambi Tue, 09/25/2007 - 00:41
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what Kind of impact are you talking about ??

Can you let me know ...Does it increase the CPU or memory in any ways..

Kevin Dorrell Mon, 09/24/2007 - 23:56
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What platform is this on? Depending on the platform, you may be able to do it with the standard MQC QoS tools. Define a class for the multicast, use the class in a policy-map that polices the traffic in that class, and apply that service-policy to the VLAN interface.

If you apply it to the VLAN interface, however, it will not affect the multicast within the VLAN itself.

I say depending on the platform, because you need a platform that supports that feature, and does so without making your CPU problems worse.

One other thought - are you doing IGMP snooping on a platform that does not support it in hardware? IGMP snooping in software is extremely CPU intensive. If that is the case, you might be better off switching to the older CGMP technology.

Kevin Dorrell



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