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November 26th, 2003 13:00
3348 Configuration Help
I have 2 stacked 3348 switches and am seeking to optimize performance. They are replacing 4 - 24 port 3Com hubs. Requests are being broadcasted across the network. What is the best and easiest way to eliminate broadcasts, other than creating VLANs? I've enabled IGMP Snooping. Will this help?
Many advanced thanks,
Keith.....
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Andrew_Hicks1
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November 26th, 2003 13:00
IGMP snooping is helpful, but only in terms of dealing with multicasts crossing the switch.
Really, your first step should be to identify what kind of traffic is crossing the network. A switch's forwarding table is great for eliminating a lot of broadcasting that you'd get with a hub, but only if the traffic in question is unicast (or multicast with IGMP snooping enabled). Use of the port mirroring function on the 3348 and a packet sniffer for just a short while should provide you with the information you need.
If you monitor the traffic crossing the switch, and it's all broadcast traffic (usually a destination MAC of FF:FF:FF:FF:FF:FF or any destination IP address ending in .255), there's not much the switch can do *but* broadcast. You then might want to look at the protocols involved, and see if they should be passing on the network, or if they need to be eliminated.
One other option you have, is broadcast storm control - however, this feature is only useful if you have broadcast traffic that exceeds a certain threshold, after which the switch will stop forwarding broadcasts, until the traffic drops below the threshold again.