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Total of CBWFQ "priority percent" and "bandwidth percent" can't reach 100%?

I have a 2811 router with the following QoS configuration. My intention is to have class INTERNET use whatever is left from other classes. Does this policy map accomplish this? I'm not sure because "show policy-map interface" doesn't show any bandwidth numbers for class INTERNET. Besides, there's also a class class-default in there too.               

--------------

policy-map QOS
class VOICE
  priority percent 20
class CONTROL
  bandwidth percent 5
class VIDEO
  bandwidth percent 30
class BUSINESS
  bandwidth percent 30
  random-detect
class INTERNET

int serial0/0/0
bandwidth 2000
max-reserve 100
service-policy out QOS

-----------------

I'm thinking to put a "bandwidth percent 15" command for class INTERNET. So it will use exactly all the remaining bandwidth. However IOS showed this error "Sum total of class bandwidths exceeds 99 percent". It only took the command "bandwidth percent 14", but in that case, the total only adds up to 99%.

My question is: (1) does the policy-map mean class INTERNET can use whatever is left from other classes? (2) if to have a bandwidth command for class INTERNET, is it IOS behavior to have total only to 99%?

Thanks

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4 REPLIES 4
VIP Expert

Re: Total of CBWFQ "priority percent" and "bandwidth percent" ca

Hi,

My question is: (1) does the policy-map mean class INTERNET can use whatever is left from other classes?

Yes, the remaining bandwidth (in this case 15 percent) goes to class-default (Internet)  If class-default is not using it, than the other classes can use it.

Here is doc for more info:

http://www.cisco.com/en/US/tech/tk543/tk757/technologies_tech_note09186a0080103eae.shtml

(2) if to have a bandwidth command for class INTERNET, is it IOS behavior to have total only to 99%?

The total sum should be at 100% not 99.

here is your sample config with Internet having 15%

policy-map qos

class voice

  priority percent 20

class control

  bandwidth percent 5

class video

  bandwidth percent 30

class business

  bandwidth percent 30

class internet

  bandwidth percent 15

HTH

VIP Expert

Re: Total of CBWFQ "priority percent" and "bandwidth percent" ca

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

What you might be bumping into is a need for 1% of bandwidth being available for class-default (which is always present, even when not explicitly defined).  Bandwidth allocation rules vary a little on your installed IOS, i.e. whether it's pre or post HQF.

Bandwidth statements set a "floor" bandwidth.  Any unused bandwidth is available to outer non-LLQ classes.  (If more than one class wants the excess available bandwidth, they will share it in the same ratios as their bandwidth statements are configured.)

(Note: LLQ classes are a little different as the priority statement defines an implicit policer.)

Explorer

Re: Total of CBWFQ "priority percent" and "bandwidth percent" ca

I'm using IOS 12.4(24)T2. The router is 2811. The WAN interface is Frame-relay. Is 1% bandwidth required for class class-default in Cisco publications? I did a brief search of Cisco documentations but didn't find any.

In my config, is it precise to say "class INTERNET and class class-default will use whatever bandwidth is remaining from other classes"? When I tried "class INTERNET, bandwidth percent 15", IOS didn't accept it. If class class-default does require a minimum 1% bandwidth, this would make sense, because class-default can't be deleted.

policy-map QOS
class VOICE
  priority percent 20
class CONTROL
  bandwidth percent 5
class VIDEO
  bandwidth percent 30
class BUSINESS
  bandwidth percent 30
  random-detect
class INTERNET

VIP Expert

Re: Total of CBWFQ "priority percent" and "bandwidth percent" ca

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

Your version of IOS, I believe, is the HQF version.  If I also recall correctly, in HQF, class-default does require a minimum of 1%.  (NB: other ways to confirm yours is HQF, max-reserve isn't necessary under the interface and other non-LLQ classes will accept fair-queue statement.)

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