Task 6.1 - Rate-Limit

Hi all,

I'm struggling to work out how the SG got 10000 bytes for Normal-Burst and Burst-Max.

I use the formula Bc=CIR*(Tc/1000) and Be=(AIR-CIR)*(Tc/1000) to work out these out however the answers doesn't match up with the SG...

rate-limit input access-group 191 8000 10000 10000 conform-action transmit exceed-action drop

I've tried to seek this in CiscoDoc and INE Advance Tech Videos and I'm not having any luck.

Help!

Comments

  • Could you paste the full question so we can take a look? Sorry I don't have access to the mock lab questions.

  • The question..

    6.1. Traffic Filtering

    • Administrators of your network are concerned about Ping of Death attacks coming in from BB2. In order to minimize the risk of these attacks configure R2 to accept a maximum of 8Kbps of ICMP traffic in from BB2.

    • Do not use MQC syntax to accomplish this.

    INE Answer...

    R2:

    interface FastEthernet0/0

    rate-limit input access-group 191 8000 10000 10000 conform-action transmit exceed-action drop

    !

    access-list 191 permit icmp any any

     

  • interface FastEthernet0/0

    rate-limit input access-group 191 8000 10000 10000 conform-action transmit exceed-action drop

    It's fairly straight forward to answer this task since you are asked to limit the ping up to 8 Kbps, i.e. 8000 bps & the minimum burst i.e. 1000 bytes. The traffic type "ICMP" has been mentioned in the ACL 191.

    HTH

  • I agree this is a simple task. INE used 10000 bytes which is not the minimum. It would not accept the minimum 1000 as you'll get an error. I guess these figures can be anything as long the first is 8000 as the task does not specify anything for these burst. 

  • I guess these figures can be anything as long the first is 8000 as the task does not specify anything for these burst. 

    Yes, you are right. If you look into the context sensitive help, you may see the following option for maximum burst bytes:

    R1(config-if)#rate-limit input 8000 1000 ?

      <2000-1024000000>  Maximum burst bytes

    If i'm not wrong, it could be just because of IOS variation or there might be error in the solution.

    Please check it once & get back to us what output you got. Also, I believe that you can give any value as burst if you are not told explicitly for any specific value.

    Good luck!

     

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