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Tuesday, October 26, 2010

Question 156

You must ensure that traffic that is IP precedence 5 is limited to 128000 bps has a burst size of 24000 to 32000. Conform action should be forwarded as is and exceeded traffic should be marked IP precedence 3.

You cannot use CQ, PQ or MQC.

4 comments:

networkdongle said...

my weak spot is QoS, correct answer based of the wording i keyed on was "limited to 128000bps"

'rate-limit input dscp 40 128000 2400 3200 conform-action transmit exceed-action set-dscp-transmit 24'

dscp CS5 decimal 40 binary 101000 = IP Precedence/ToS 101 (5) - Critical

dscp CS3 decimal 24 binary 011000 = IP Precedence/ToS 011 (3) - Flash

so should get it done...

networkdongle said...

another look at the config guide showed me this way to do, i still think my first way would word as well, but this might be more exact, well either one of these ways i do not see or know the difference using the rate-limit acl:

rate-limit input access-group 101 128000 2400 3200 conform-action transmit exceed-action set-prec-transmit 3
access-list 100 permit ip any any precedence critical



access-list rate-limit 1 5
rate-limit input access-group rate-limit 1 128000 2400 3200 conform-action transmit exceed-action set-prec-transmit 3

Packets Analyzed said...

I think here you are relying on CS/IP Prec/DSCP mappings in order to achieve the requirement. I am really not sure that you want to rely on this as you would have to confirm that the mappings are accomplishing the desired results. Based on default mappings you would have accomplished the requirement indirectly so I am not sure if you would have received the points.

Good work in breaking this apart

Packets Analyzed said...

My last comment was for your initial response.

You last response is what I was looking for which guarantees that you meet the requirement and you are not dependent on additional configuration to ensure that you achieve the results.

rate-limit input access-group 101 128000 2400 3200 conform-action transmit exceed-action set-prec-transmit 3
access-list 100 permit ip any any precedence critical

access-list rate-limit 1 5
rate-limit input access-group rate-limit 1 128000 2400 3200 conform-action transmit exceed-action set-prec-transmit 3

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