Re: Storm control in 3550 and 3560 switches

Hi Darby,

  Thank you very much for the descriptive explanation on the topic.Not sure
I understood the below caveat

 "If you enable broadcast and multicast traffic storm control, and broadcast
traffic exceeds the level within a 1-second traffic storm control interval,
traffic storm control drops all broadcast and multicast traffic until the
end of the traffic storm control interval. "

Is that mean that,if the broadcast traffic exceeds the threshold level,it
will also drop multicast traffic,when the multicast didn't eceed the
threshold defined on the later 2 interface ??/..Is it true for both 3550 and
3560 switches ?

Thank you

Regards
Anantha Subramanian Natarajan

On Mon, Sep 14, 2009 at 5:05 AM, Darby Weaver <darby.weaver_at_gmail.com>wrote:

> Some caveats you may to take note of on Storm-Control:
>
> All Layer 2 Broadcasts are Multicasts.
>
> All Layer 2 Multicasts are *not* Broadcasts.
>
> Traffic storm control monitors the level of each traffic type for which you
> enable traffic storm control in 1-second traffic storm control intervals.
> Within an interval, when the ingress traffic for which traffic storm
control
> is enabled reaches the traffic storm control level that is configured on
the
> port, traffic storm control drops the traffic until the traffic storm
> control interval ends.
>
> The following are examples of traffic storm control behavior:
>
> If you enable broadcast traffic storm control, and broadcast traffic
> exceeds the level within a 1-second traffic storm control interval, traffic
> storm control drops all broadcast traffic until the end of the traffic
storm
> control interval.
>
> If you enable broadcast and multicast traffic storm control, and the
> combined broadcast and multicast traffic exceeds the level within a
1-second
> traffic storm control interval, traffic storm control drops all broadcast
> and multicast traffic until the end of the traffic storm control interval.
>
> If you enable broadcast and multicast traffic storm control, and
> broadcast traffic exceeds the level within a 1-second traffic storm control
> interval, traffic storm control drops all broadcast and multicast traffic
> until the end of the traffic storm control interval.
>
> If you enable broadcast and multicast traffic storm control, and
> multicast traffic exceeds the level within a 1-second traffic storm control
> interval, traffic storm control drops all broadcast and multicast traffic
> until the end of the traffic storm control interval.
>
> 1) One very important remark everybody seems to miss, is that storm-control
> only works on INBOUND packets. It does not prevent a port from being
> overwhelmed with broadcasts from the core or other access switches.
>
> 2) Watch out with stormcontrol on trunk ports! Includes any allowed or
> non-allowed Vlan
>
> 3) The storm-control "drop filter" action will block on all VLANS.
>
> Finally:
>
> Storm control is supported only on physical interfaces; it is not supported
> on EtherChannel port-channels or physical interfaces that are members of
> port channels even though the command is available in the CLI. If a
physical
> interface with storm control configured joins an EtherChannel, the storm
> control configuration for the physical interface is removed from the
running
> configuration.
>
>
>
>
>
> On Sun, Sep 13, 2009 at 8:01 PM, Anantha Subramanian Natarajan <
> anantha.natarajan_at_gravitant.com> wrote:
>
>> Hi All,
>>
>> My understanding on ,Multicast storm control on 3550 switch is as below
>>
>> "When the rate of multicast frames increased more than the specified
>> rate
>> on the Multicast storm-control configuration,it will block all multicast
>> frames exceeded and also even all unicast/broadcast traffic is dropped
>> until
>> the multicast rate on the port is decreased than the threshold
>> defined.Exceptions would be BPDU's and CDP frames".
>>
>> Is my above understanding right ?.If so ,my questions is
>>
>> Does the above statement is also true for 3560 switches.For some reason.I
>> couldn't find a reference on the 3560 config guide,unless I missed it.
>>
>> Thank you for the assistance.
>>
>> Regards
>> Anantha Subramanian Natarajan
>>
>>
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>>
>
>
> --
> Darby Weaver
> Network Engineer
>
> 407-802-7394
> darbyweaver_at_yahoo.com

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Received on Mon Sep 14 2009 - 05:41:22 ART