Re: Storm control in 3550 and 3560 switches

Thank you Scott

Regards
Anantha Subramanian Natarajan

On Mon, Sep 14, 2009 at 11:47 AM, Scott Morris <smorris_at_ine.com> wrote:

> Correct. unicast = 0, multicast AND broadcast = 1.
>
>
>
>
> *Scott Morris*, CCIE/x4/ (R&S/ISP-Dial/Security/Service Provider) #4713,
>
> JNCIE-M #153, JNCIS-ER, CISSP, et al.
>
> JNCI-M, JNCI-ER
>
> evil_at_ine.com
>
>
> Internetwork Expert, Inc.
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> Power corrupts.
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>
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>
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>
> Anantha Subramanian Natarajan wrote:
> > Hi Scott,
> >
> > Thank you very much for the descriptive explanation/history.This is
> > actually a recap for me after I have heard your audio series soo many
> times
> > but somehow I understood that even unicast(In that case,As I understood,I
> > would assume the I/ G bit would be 0 right,where for multicast/broadcast
> > would be 1) is dropped after the multicast threshold is reached in
> > 3550.Kindly correct me if I am wrong in that.If thats true, is it true
> even
> > in 3560 switches.
> >
> > Thank you Scott
> >
> > Regards
> > Anantha Subramanian Natarajan
> >
> >
> >
> > On Mon, Sep 14, 2009 at 8:56 AM, Scott Morris <smorris_at_ine.com> wrote:
> >
> >
> >> Other way around. Broadcasts are a SUBSET of multicasts.
> >>
> >> At layer2, a multicast is defined by the I/G bit. The least significant
> >> bit of the most significant byte of a MAC.
> >>
> >> For example, all IP multicast at layer2 begins with 01-00-5E-xx-xx-xx.
> >> 01 is the most significant byte (left-most). In binary it's 0000 0001.
> >> The 1 is the least-significant bit (right-most) of this byte. That's
> >> the I/G bit. A 1 value indicates a GROUP address while a 0 value
> >> indicates an INDIVIDUAL address (the I and the G).
> >>
> >> A broadcast at layer2 is FF-FF-FF-FF-FF-FF. Or in binary, 1111 1111 in
> >> the most significant byte. Being all-ones, it's a very specific
> notation.
> >>
> >> Not all multicasts can be called broadcasts. But all broadcasts can
> >> also be called multicasts (group addresses).
> >>
> >> So if you have a storm control threshold of 10% for multicast, but 20%
> >> for broadcast... Once you hit your 10% mutlicast mark, your broadcasts
> >> will get throttled as well since they are part of that same group.
> >>
> >> It's all about perspective (and a little history). ;)
> >>
> >> HTH,
> >>
> >>
> >>
> >>
> >> *Scott Morris*, CCIE/x4/ (R&S/ISP-Dial/Security/Service Provider) #4713,
> >>
> >> JNCIE-M #153, JNCIS-ER, CISSP, et al.
> >>
> >> JNCI-M, JNCI-ER
> >>
> >> evil_at_ine.com
> >>
> >>
> >> Internetwork Expert, Inc.
> >>
> >> http://www.InternetworkExpert.com <http://www.internetworkexpert.com/><
> http://www.internetworkexpert.com/>
> >>
> >> Toll Free: 877-224-8987
> >>
> >> Outside US: 775-826-4344
> >>
> >>
> >> Knowledge is power.
> >>
> >> Power corrupts.
> >>
> >> Study hard and be Eeeeviiiil......
> >>
> >>
> >>
> >>
> >>
> >> Anantha Subramanian Natarajan wrote:
> >>
> >>> 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
> >>>>>
> >>>>>
> >>>>> Blogs and organic groups at http://www.ccie.net
> >>>>>
> >>>>>
> _______________________________________________________________________
> >>>>> Subscription information may be found at:
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> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>> --
> >>>> Darby Weaver
> >>>> Network Engineer
> >>>>
> >>>> 407-802-7394
> >>>> darbyweaver_at_yahoo.com
> >>>>
> >>>>
> >>> Blogs and organic groups at http://www.ccie.net
> >>>
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Received on Mon Sep 14 2009 - 11:48:14 ART