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Santosh Shetty
Beginner

shape average command

            class FTP

                 shape average percent 28

                 shape avergae 25

                 bandwidth percent 26

if shape command define Max BW limit and bandwidth percent command define Min BW, how these command will work?

5 REPLIES 5
nkarpysh
Cisco Employee

Hi Santosh,

The thing is that bandwidth command reserve bandwidth for the time of congestion. If there is no congestion on the interface then particular class can go  higher than the bandwidth value configured and kinda ignore it. If congestion happens then bandwidth command guarantee to provide at least this amount of traffic to go through.

Shape as you said is maximum  - if there is no congestion, shape will still limit traffic to what is configured using shaping mechanisms.

You can find more specifics of shaping here:

http://www.cisco.com/en/US/tech/tk543/tk545/technologies_tech_note09186a00800a3a25.shtml

http://www.cisco.com/en/US/docs/ios/12_2/qos/configuration/guide/qcfcbshp.pdf

http://www.cisco.com/en/US/docs/ios/12_1t/12_1t2/feature/guide/clsbsshp.html

Nik

HTH,
Niko

Nik,

Thanks for links, so as per above example, class FTP will get only 25% BW during congestion & and non congestion. It will never cross 25% and bandwidth pecent 26 will not play any role.

Hi

As far as I know there is no command like " shape average percent 28", at least on the platforms I worked with. Will be glad to check if you have some docs for that.

So I think what will work is only this:

shape avergae 25

bandwidth percent 26

The thing is that shape average X shape not on percentage but on exact CIR value in bps, so this class will be shaped for 25 bps and never come up to 26% of the interface bandwidth.

Nik

HTH,
Niko

Nik,

Found that command on 1721 router

Router(config-pmap-c)#shape average percent ?

  <1-100>  Percentage

http://www.cisco.com/en/US/docs/ios/12_2t/qos/command/reference/qftcmd9.html

EX. So if CIR is 1000000 (1Mb)

shape average 200000

bandwidth 100000

will mean during with no utilization - traffic will able to reach upto 200 Kb and in congestion it will get minimum BW of 100 kb, so is that correct.

Thanks Santosh,

good also to learn some commands.

Yes - your understanding is correct. Bandwidth command will provide garantee amount during congestion and shape will provide maximum for all the time.

Nik

HTH,
Niko