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Storm Control on Port-Channel Interfaces (6500 platform)


I cannot find it anywhere in the documentation for the Cisco 6500 platform (IOS). The question is this: When calculating the percentage of broadcast passing through a Port-Channel interface, which total bandwidth figure is used by the switch? For example:

a. If we have a bundle of 4 Gig interfaces in a PortChannel with Storm-Control applied, the threshold will be calculated over 4Gb/s or 1Gb/s?

b. If the same PortChannel for some reason loses 2 of the uplinks in the Bundle, will the calculation be made over 4Gb/s, 2Gb/s or 1Gb/s?



Storm Control on Port-Channel Interfaces (6500 platform)

Hi Leo,

I can't find any reference to this at the moment, but my thoughts are that it will be based on a single member port of the port-channel.

Remember that a port-channel is logically a single link and so a broadcast is only sent on one of the links of the port-channel and not all of them. The decision as to which link is used will be the same as for any other frame i.e., the broadcast address is used within the hashing calculation to choose the physical port.

If the storm-control values are determined based upon the aggregate bandwidth, and changes as links are added/removed from the agregate, then the suppression threshold values for link carrying the broadcasts is never going to be correct.


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