difference between rate-limit and policy command?

[libincisco]

I can not tell the difference between them except their configuration mode.

I mean in most circumstances, this two method can fit for with no difference. Am I right?

[beng]

Policy used to specify different classes and how the traffic will be treated in the different class. Rate-limit is just for a specific interface, no classification of the traffic.

Example:

router(conifig)#class-map CLASSNAME

router(config-cmap)#match any

router(config-cmap)# exit

router(config)#policy-map POLICYNAME

router(config-pmap)#class CLASSNAME

router(config-pmap-c)#bandwidth

if you'd like a more smooth dropping of packets you can configure WRED on this policy-map

router(config-pmap-c)#random-detect

Then apply the service policy on the interface:

Router(config-if)#service-policy [in | out] POLICYNAME

~~~~~~~~~~~~~~~~~~~~~~

Rate-limit in CAR:

You can take a look at that technology here:

http://www.cisco.com/cpropart/sync-src/ccstcp/cc/pd/iosw/tech/carat_wp.htm

The CAR command-line syntax follows:

Rate-limit {input | output}

[ access-group [rate-limit] ]

conform-action {drop|transmit|continue|set-prec-transmit |

set-prec-continue }

exceed-action {drop|transmit|continue|set-prec-transmit |

set-prec-continue }

Where normal burst = r * 1byte/8bits * 1.5 seconds, where r is configured rate extended burst = 2 *

normal_burst

For example... to limit the outbound traffic on your ethernet0 interface to 4.5Mb. I'd go to that

interface configuration mode and type:

Router(config-if)#rate-limit output 4500000 24000 32000 conform-action transmit exceed-action drop

Hope these helps.

/beng

[libincisco]

I think sometimes these two methods can be exchanged, ok?

[CHRISTOPHER LARSON]

You are correct. They are different methods for doing the same thing. Policing traffic. They can be used interchangeably. Using MQC and policy/class maps allows the most options and greater flexability and is what I prefer.

[libincisco]

thank you very much