From: Pavel Bykov (slidersv@gmail.com)
Date: Fri Feb 27 2009 - 09:23:39 ARST
We had a discussion about this a while ago, and because matters are much
more deep and complicated, I had to carry out some testing.
Here are the answers to "max-reserved-bandwidth" and 75/25% myth:
http://www.boxoid.org/cisco/MAX-RESERVED-BANDWIDTH-AND-CBWFQ.pdf
Especially check out chapter 6. Also, the documentation pertaining to this
is changing, and so is the behaviour in different IOSes.
On Fri, Feb 27, 2009 at 10:19 AM, Nadeem Ansari
<nadeem.ansari574@gmail.com>wrote:
> Control traffic does not fall in class-default as per my understanding,
> Remaining bandwidth other than reservation will be used for routing
> protocols and other control traffic.
>
> Class-default is unspecified user traffic, but there is one catch whatever
> QoS you do your control traffic will take preferance over your other
> defined
> and undefined traffics.
> Hope somebody correct me if I am wrong :)
>
> Regards
> Nadeem
>
> On Fri, Feb 27, 2009 at 2:25 PM, Ali Simaan <alisimaan@gmail.com> wrote:
>
> > Hi All
> >
> > I am confused about this CBWFQ logic.
> >
> > In all Cisco QOS Documentation they state that when adjusting an
> interfaces
> > max-reserved bandwidth above 75% extreme caution is required to ensure
> that
> > one leaves enough remaining bandwidth to support best effort, control and
> > layer 2 overhead traffic. I understand that all unclassified traffic is
> > assigned to the class-default class. However is the control and layer 2
> > overhead traffic also assigned to the class-default class or does it sit
> > somewhere else?
> >
> > If i configure a router as below and have reserved 100% of the interface
> > bandwidth and assigned class-default 25%, is the control and layer 2
> > overhead traffic actually still getting the same kind of service, or are
> > there risks with this configuration?
> >
> >
> >
> >
> > interface Serial0/0
> > bandwidth 128
> > ip address 131.1.12.1 255.255.255.0
> > max-reserved bandwidth 100
> > service policy output QOS
> >
> >
> > policy-map QOS
> > class 1
> > bandwith percent 75
> >
> > class class-default
> > bandwidth percent 25
> >
> >
> >
> >
> > Also how would the cbwfq logic work if i had only assigned 20 percent to
> > the
> > class-default class? Where would the other 5 % that is not assigned to
> any
> > class sit and what would be assigned to it?
> >
> >
> > Hope someone can shed some light on this.
> >
> > Thanking you in advance
> > Ali
> >
> >
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> >
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>
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>
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>
>
-- Pavel Bykov ---------------- Don't forget to help stopping the braindumps, use of which reduces value of your certifications. Sign the petition at http://www.stopbraindumps.com/Blogs and organic groups at http://www.ccie.net
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