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Hi,

Just wondering if anyone else decided to use the rate-limit command to do this task and compare solution with me. I did:

access-list 101 permit icmp any any

int f0/0

   rate-limit output access-group 101 128000 4000 4000 conform-action transmit exceed-action drop

Hi,

Yes I also decided to use the rate-limit command and my config is identical to yours. It must have been the title of the task "Rate Limiting" that led me to use it instead of a service policy.

Does anyone know if there is a reason why we should not use rate-limit to complete this task?

Hi,

    In this particular task you can use rate-limiting as long as you make use of the standard token bucket scheme, where Bc=Be. This the case where clarifications from proctor are valuable if obtained :)

Regards,

Hi,

in my opinion the information "Allow for a burst of 1/4t of this rate." does not lead to Bc=Be=4000.

In the description there is no information as to which Tc to assume. So assuming Tc=1sec leads to Bc=16000. The burst would be achieved by setting Be=16000*1/4=4000. This leads to the folling config:

police cir 128000 bc 16000 4000

What is wrong with this?

The core problems with the sentence "Allow for a burst of 1/4t of this rate." seem to be

1. What is meant by "burst"? Bc or Be?

2. It gives the burst value in bits/sec instead of bits or bytes.

Hi,

       In order to configure the policer you need to know two out of the following three values: CIR,Tc,Bc; now if you read the task again, i think it makes sense that 1/4th of this rate is the Bc; and since there is nothing specified about extended burst-Be, you either don't configure it (so use standard token bucket scheme) or set Bc=Be (so use extended token bucket scheme) to actually disable the use of it.

     If you put 1/4*128000=32000bits=4000bytes, which the solution uses.

Hope it helps,

egoge:

Hi,

in my opinion the information "Allow for a burst of 1/4t of this rate." does not lead to Bc=Be=4000.

In the description there is no information as to which Tc to assume. So assuming Tc=1sec leads to Bc=16000. The burst would be achieved by setting Be=16000*1/4=4000. This leads to the folling config:

police cir 128000 bc 16000 4000

What is wrong with this?

 

The core problems with the sentence "Allow for a burst of 1/4t of this rate." seem to be

1. What is meant by "burst"? Bc or Be?

2. It gives the burst value in bits/sec instead of bits or bytes.

 

Hm, in your interpretation of the task description you ignore the unit of CIR by using the value as "bits" instead of bist/sec (the correct unit of CIR).

Will we have to expect such a task description in the real lab?

Hi,

   Hmmm...I'm not sure what you mean; The task says 128Kbps of ICMP traffic.

Regards,

Yes, the task says Bc=CIR/4=128000/4bits/s=32000bits/sec.

However, Bc is supposed to be a value in bits or bytes, and NOT in bits/sec. Therefore, the task description is wrong.

Hi,

   The task is not wrong; it gives you the Bc in bits and you need to convert it in bytes; this is actually a common Cisco stuff seen in the lab where they give you values in bits but the router needs it to be entered in bytes.

  As a general rule, don't expect to get in the lab the EXACT thing you need to configure on the router; you may need to do this kind of conversions.

Hope it helps,

egoge:

Yes, the task says Bc=CIR/4=128000/4bits/s=32000bits/sec.

However, Bc is supposed to be a value in bits or bytes, and NOT in bits/sec. Therefore, the task description is wrong.

Hi,

sorry, I think my last post was misunderstood. I don't care about converting from "bits" to "bytes". But I cannot convert from "bits/sec" to "bytes".

cristian.matei:

The task is not wrong; it gives you the Bc in bits

No, the task gives the Bc in "bits/sec", which cannot be converted to bytes without assuming some time value (duration of the burst). You seem to assume a burst duration of 1sec. Are we supposed to do that in the real labs?

Regards,