8.2 Rate Limiting

Hi All,

 

I have quick question regarding this task.

One of your NOC engineers has noticed suspiciously high utilization on
the Ethernet segment of R1. After further investigation you have found that
a large number of ICMP packets have been traversing this link.
In order to alleviate congestion configure R1 so that it does not send more
than 128Kbps of ICMP traffic out this interface.
Allow for a burst of 1/4th of this rate.

 

Is it valid configuration

Rack1R1#sh run | sec policy
policy-map ICMP
 class ICMP
   police rate 128000 bps burst 4000 bytes
 service-policy output ICMP

Regards,

Marcin

 

 

 

Comments

  • Hi Marcin,

    This is correct. If you are provision a CIR of 128000 bps and you only want to allow a burst rate of 1/4th of that. That would lead to a burst value of 32000 bps. One thing you need to bear in mind is that the burst information uses bytes intead of bits, so you have to divide that by 8, arriving at 4000 bytes for the burst parameter.

    So your math is correct, but always remember to use the question mark to check if you need to enter a value in bits vs bytes.

    HTH

    Good luck with your studies!

  • Hi All,

     

    I have quick question regarding this task.

    One of your NOC engineers has noticed suspiciously high utilization on
    the Ethernet segment of R1. After further investigation you have found that
    a large number of ICMP packets have been traversing this link.
    In order to alleviate congestion configure R1 so that it does not send more
    than 128Kbps of ICMP traffic out this interface.
    Allow for a burst of 1/4th of this rate.

    Is it valid configuration

    Rack1R1#sh run | sec policy
    policy-map ICMP
     class ICMP
       police rate 128000 bps burst 4000 bytes
     service-policy output ICMP

    Regards,

    Marci

    This is a valid configuration if you also have class ICMP matching ICMP traffic either via access list or NBAR

  • Yes I have but the main concern I have is distinguish between policy cir and
    policy rate. Both these command do the same however I was wondering which one
    of them is better to use.

     

    Also I know that policy rate is mainly for control plane and policy rate for
    data.

     

    Regards,

     

    Marcin

  • Hi,

    The police cir is more commonly used as per my experience. I usually use police rate when I want to limit the pps (packets per second).

    HTH

    Good luck!

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