Sec 7.2 Rate Limiting

Dear All,

            The question says that to allow burst of 1/4 th of this rate (128Kbps)

So should the Bc here is equal to 128000/4 = 32000 not 4000 as in the solution guide

So the configuration must be as below

R1#sh policy-map ICMP
  Policy Map ICMP
    Class ICMP
     police cir 128000 bc 32000
       conform-action transmit
       exceed-action drop


Please Advice

Thanks In Advance


  • the BC value is entered in bytes not bits in the police command, so 32000/8 = 4000.

  • Thanks but the Bc is entered in bits not bytes


    1800-R5(config-map-class)#frame-relay bc ?
      <300-16000000>  Applied to both Incoming/Outgoing Bc, Bits
      in              Incoming Bc
      out             Outgoing Bc

    Please Advice




  • you're inside map-class frame-relay config, not policy-map config....
    you're first example was within a policy-map ICMP.

    Rack1R1(config)#policy-map TEST   
    Rack1R1(config-pmap)#class class-default
    Rack1R1(config-pmap-c)#police cir 256000 bc ?
      <1000-512000000>  Burst bytes
      conform-action    action when rate is less than conform burst
      pir               Peak Information Rate



  • Regardless of the OP's confusion on bits vs. bytes, I still have a problem understanding this one...  It appears to me that the solution at the end of the pdf of: "police cir 128000 bc 4000" is setting up rate limiting using a CIR of 128000 and a bc of 4000bytes/32000bits, thus ending up with a calculated Tc of 250ms.  And this set up should not allow bursting past CIR at all, as there is no Be configured.

    Im thinking that maybe where Im going wrong here is that in the case of non frame-relay rate limiting, there is no concept of a Tc??? And that in this case, you just specify the base CIR you want, and the bc is NOT used as part of the CIR&Tc calc, but is instead used to calculate what you burst ABOVE the CIR, whereas with frame relay, the Bc is used as PART of the CIR/Tc calculation?


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