From: Scott Morris (swm@emanon.com)
Date: Mon Nov 01 2004 - 10:42:58 GMT-3
Looking at your first policy:
policy-map CBWFQ
class queue1
bandwidth percent 22
class queue2
bandwidth percent 7
class queue3
bandwidth percent 37
class queue4
bandwidth percent 34
Those values add up to 100. In 12.2, that will reserve 100% of the
AVAILABLE bandwidth (75% of line bandwidth). So if you had a 1 Mb line,
that would reserve 100% of 750K. There still would be 25% leftover for
'unclassified traffic' which is automatically considered to be
class-default.
In your second policy:
policy-map CBWFQ
class queue1
bandwidth percent 22
class queue2
bandwidth percent 7
class queue3
bandwidth percent 37
class queue4
bandwidth percent 22
class class-default
bandwidth percent 12
You actually specify the class-default configuration. This is acceptable,
but bear in mind that without the setting your max-reserved-bandwidth to
100% on the interface, you aren't accomplishing as much as you would think!
You're giving a guarantee, but a pseudo-limit in weighted round robin
scheduling by giving a number to the class-default while not changing other
default behaviors.
As far as which one is correct, that will entirely depend on how your lab is
worded! If you are told to give certain guarantees to otherwise
unclassified traffic, then you should specify stuff for the class-default.
If not, leave it alone! Think through what the router will be
doing/thinking and that should help answer the question!
HTH,
Scott
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Swaroop Potdar
Sent: Monday, November 01, 2004 8:23 AM
To: swm@emanon.com; ccielab@groupstudy.com
Subject: RE: CBWFQ Percentage Calculation Doubt
Hi Scott,
Thanks for your reply....though still have a doubt would appreciate some
more of your time
I am pasting the config below..is the interface config correct i mean can we
do reserved bandwidth 100% and if we do so do we have to consider some space
for the default class....and on the same interface i have given two
different service policy variations config which one is correct ?
the one without default class or the one with it. as there is a default
class by default is it mandatory to use and allocate some percentage or
leave aside some percentage for it.
--------------------------------------------------------
interface Ethernet0/0
ip address 133.1.23.2 255.255.255.128
ip nbar protocol-discovery
ip pim sparse-mode
max-reserved-bandwidth 100
service-policy output CBWFQ
half-duplex
end
1)
class-map match-all queue1
match protocol telnet
class-map match-all queue3
match protocol http
class-map match-all queue2
match protocol ftp
class-map match-all queue4
match protocol dlsw
!
!
policy-map CBWFQ
class queue1
bandwidth percent 22
class queue2
bandwidth percent 7
class queue3
bandwidth percent 37
class queue4
bandwidth percent 34
!
or
2)
class-map match-all queue1
match protocol telnet
class-map match-all queue3
match protocol http
class-map match-all queue2
match protocol ftp
class-map match-all queue4
match protocol dlsw
!
!
policy-map CBWFQ
class queue1
bandwidth percent 22
class queue2
bandwidth percent 7
class queue3
bandwidth percent 37
class queue4
bandwidth percent 22
class class-default
bandwidth percent 12
!
-----------------------------------------
>From: "Scott Morris" <swm@emanon.com>
>Reply-To: "Scott Morris" <swm@emanon.com>
>To: "'Swaroop Potdar'" <swarooppotdar@hotmail.com>,
><ccielab@groupstudy.com>
>Subject: RE: CBWFQ Percentage Calculation Doubt
>Date: Mon, 1 Nov 2004 08:08:47 -0500
>
>In 12.1, the percentage was calculated based on interface bandwidth,
>allowed
>to a max additive value of 75%.
>
>In 12.2, this was changed to calculate based on "available bandwidth",
>which
>was a pre-calculated value of 75% of the line bandwidth. So you could
>reserve 100% of this amount.
>
>HTH,
>
>
>Scott Morris, MCSE, CCDP, CCIE4 (R&S/ISP-Dial/Security/Service Provider)
>#4713, JNCIP, CCNA-WAN Switching, CCSP, Cable Communications Specialist, IP
>Telephony Support Specialist, IP Telephony Design Specialist, CISSP
>CCSI #21903
>swm@emanon.com
>
>
>
>
>-----Original Message-----
>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>Swaroop Potdar
>Sent: Monday, November 01, 2004 6:16 AM
>To: ccielab@groupstudy.com
>Subject: CBWFQ Percentage Calculation Doubt
>
>Hi Group,
>
>I wanted to confirm this doubt about CBWFQ,
>
>-----------------
>
>If in a question the default queue size to be used is not given
>
>then;
>
>do we have to do the bandwidth calculation without factoring the
>max-reserved-bandwidth.
>
>and if the default queue size for the traffic is given
>
>then
>
>we have to do the bandwidth percentage calculation as 100% of the interface
>bandwidth
>
>?????
>
>
>
>Regards,
>Swaroop
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Regards,
Swaroop.
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