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Broadcast/Multicast Best Practice Limits

I have not been able to find consistant rules regarding the amount of broadcast and multicast traffic on a given switch port. The original rule was "Broadcasts should not exceed 40 per second", then other rules say "Broadcast and Multicast traffic should not exceed 100 (or even 120) per second". What is Cisco's (or other's) official and unofficial view towards this subject? I know that it depends on characteristics of the server itself (CPU, etc.), but can we make a generalizations about servers produced now, which are a lot more powerful (more CPU, more RAM, etc) than those produced a few years ago (obviously)?

For instance, if I have a new server, and I see the bandwidth on its 100-Full connection is around 5%, how many b-cast/m-cast can occur before being an issue? If that same server's bandwidth utilization was 30%, then what should the b-cast/m-cast limit be?

The main reason for the question is that one of our networks has grown large and we are planning to reduce its size, but we want to carefully plan which servers are moved off. We have a very isolated issue with complaints of slowness on our Cat6509 - on a few new servers that do not exceed more than 5% bandwidth utilization for their ports. I would just like some docs that agree that says a certain amount of b-cast/m-cast should not slow down a new server with that little of traffic on it. Thanks!


Re: Broadcast/Multicast Best Practice Limits

I do not think there is any prescribed limit on this and the amount of broadcast/multicast that one has varies from network to network. Based on your network pattern and conditions, you can tune the amount of this traffic per port. Check this URL for more details on broadcast/multicast suppression

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