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Beginner

Policing traffic on 3650x

Hi everyone,

 

I was solving problem with policing traffic a used this commands to set configuration on switch:

SW1(config)#policy-map Policy1

SW1(config-pmap)#class Class2
SW1(config-pmap-c)#police cir 4000000 conform-action transmit exceed-action drop

 

SW1(config)#interface GigabitEthernet 1/0/1
SW1(config-if)#service-policy input Policy1

 

But I have problem with receiving traffic rate, I transmitting 5000 kbps but I receiving 4640 kbps instead of 4000 kbps. Tha packets should be dropped. Thank you for your advice.

8 REPLIES 8
VIP Mentor

Re: Policing traffic on 3650x

Hello,

 

what are you matching in your class ? The service policy cannot limit the incoming traffic originating from the outside. Where are you receiving more than 4K of traffic, the router, or some end device ?

Post the full config of your switch...

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Beginner

Re: Policing traffic on 3650x

I'm sorry a forget post all config:

 

SW1(config)#class-map Class2
SW1(config-cmap)#match ip dscp af13

 

SW1(config)#policy-map Policy1

SW1(config-pmap)#class Class2
SW1(config-pmap-c)#police cir 4000000 conform-action transmit exceed-action drop

 

SW1(config)#interface GigabitEthernet 1/0/1
SW1(config-if)#service-policy input Policy1

 

I'm using generator/analyzer Spirent TestCenter1 which is generating traffic with DSCP value = AF13 (rate 5000 kbps) and I measure incoming traffic from this switch to analyzer.

VIP Mentor

Re: Policing traffic on 3650x

Hello,

 

what I meant with full configuration was the full output of the command 'sh run'...can you post that ?

 

Where is the Traffic Generator located, on another subnet ? Post a schematic drawing of your topology including the IP addresses of the traffic generator and the switch interface you have the service policy configured on...

VIP Expert

Re: Policing traffic on 3650x

Several possible answers, although I don't know if any might apply.

First, on some Cisco devices, I'm unsure policers count L2 or L3 bandwidth. If the Cisco switch is counting L3 and your test equipment is counting L2, the latter would be higher.

Second, there's the issue of what K is. I.e. 1,000 or 1,024. Such can throw off stats if one device is using "decimal" while the other device is using "binary". (If this is happening, if you can control frame size, the difference should decrease as frame size increases.)

Third, depending on Tc and frame sizes, and exactly how traffic is being placed on the wire, allowed bandwidth might vary.

Lastly (at least of the things that come to mind), Cisco's implementation might not be "precise" for some reason. For example, they mention on the original 3750 series that egress port limiting is rather inexact (which is likely due to ASIC limitations), although I don't recall a similar mention for ingress policing, perhaps there's hardware precision limitations.

Beginner

Re: Policing traffic on 3650x

I will post all config on monday because switch is in laboratory. My generator use L2 traffic with IPv4 header because of using DSCP values. I'm using this topology:

 

 I'm using MTU on L2 layer with size of 1500 B.

VIP Expert

Re: Policing traffic on 3650x

"The service policy cannot limit the incoming traffic originating from the outside."

Georg, could you further explain why not?
VIP Mentor

Re: Policing traffic on 3650x

My follow up question was to see the topology as well as the full config of the switch...sorry for the misunderstanding. It is not clear, af least to me, where the traffic is coming from ( same or different subnet) and how it hits the interface with the applied service policy...

VIP Expert

Re: Policing traffic on 3650x

Thanks.
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