rate-limit 42 mb in cisco 3845 on gi0/0 WAN interface

[csawest.dc]

Dear Experts,

I need 42 mb rate-limit on WAN interface in cisco 3845 router , i already rate-limit on sub-interface and it's working fine

e.g rate-limit input 2048000 64000 64000 conform-action transmit exceed-action drop

     rate-limit output 2048000 64000 64000 conform-action transmit exceed-action drop

same like as per given above conig which is 2 mb and brust 64000 so i need 42 mb rate-limit on wan interac with brust

i bit confuse how many brust when i rate-limit 42 mb in place of 64000 brust.

so which is the exact command 42 mb rate-limit with brust i need to apply on WAN interface.

Thanks in ADV,

[sumitava123]

Hi,

Rate limit uses token bucket algorithm. The BC or normal burst is the depth of the bucket. Packet will be transmitted if there is enough token in the bucket. The max burst is used when there is not enough token in the bucket.

When we use Rate-Limit(CAR) Cisco recomends these calculations for the normal and extended burst parameters:

Burst-normal = configured rate * 1/8 * 1.5 seconds (1/8 for convert bit to byte)

Burst-max = Burst-normal * 2

Check this link for more details.

http://www.cisco.com/en/US/docs/ios/qos/command/reference/qos_q1.html#wp1054922

I hope this can help you out

Sumit

[csawest.dc]

Dear Sumitava,

Thanks for your good explanation by given this link but there is huge in details so i again confuse.

So pease i need exact command for 42 mb rate-limit on gi wan interface

like :

rate-limit input 42mb ( ???? ) brust (???) brust (???) conform-action transmit exceed-action drop

rate-limit output 42mb ( ???? ) brust (???) brust (???) conform-action transmit exceed-action drop

Thanks in ADV,

[sumitava123 · Accepted solution]

The configuration according to cisco should be as follows but there is no hard & fast rule for BC and BE value. You can change it according to your convenience 

     rate-limit input   44040192 8257536 16515072 conform-action transmit exceed-action drop

     rate-limit output   44040192 8257536 16515072 conform-action transmit exceed-action drop

Cheers

Sumit

[csawest.dc]

Dear Sumit,

Thank you very much i will try to do this command for 42 mb rate-limit on gi int in 3845 router and then let you know.

Thanks once again!!!