Cisco Catalyst 4500 Series Configuration Manual page 588

Chapter 2
police
Token Bucket Algorithm with Two Token Buckets Example (Refer to RFC 2697)
In this particular example, Traffic Policing is configured with the average rate at 8000 bits per second,
the normal burst size at 1000 bytes, and the excess burst size at 1000 bytes for all packets leaving Gigabit
Ethernet interface 6/1.
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# class-map access-match
Switch(config-cmap)# match access-group 1
Switch(config-cmap)# exit
Switch(config)# policy-map police-setting
Switch(config-pmap)# class access-match
Switch(config-pmap-c)# police 8000 1000 1000 conform-action transmit exceed-action
set-qos-transmit 1 violate-action drop
Switch(config-pmap-c)# exit
Switch(config-pmap)# exit
Switch(config)# interface gigabitethernet 6/1
Switch(config-if)# service-policy output police-setting
Switch(config-if)# end
In this example, the initial token buckets starts full at 1000 bytes. If a 450-byte packet arrives, the packet
conforms because enough bytes are available in the conform token bucket. The conform action (send) is
taken by the packet and 450 bytes are removed from the conform token bucket (leaving 550 bytes).
If the next packet arrives 0.25 seconds later, 250 bytes are added to the conform token bucket
((0.25 * 8000)/8), leaving 800 bytes in the conform token bucket. If the next packet is 900 bytes, the
packet does not conform because only 800 bytes are available in the conform token bucket.
The exceed token bucket, which starts full at 1000 bytes (as specified by the excess burst size) is then
checked for available bytes. Because enough bytes are available in the exceed token bucket, the exceed
action (set the QoS transmit value of 1) is taken and 900 bytes are taken from the exceed bucket (leaving
100 bytes in the exceed token bucket.
If the next packet arrives 0.40 seconds later, 400 bytes are added to the token buckets ((.40 * 8000)/8).
Therefore, the conform token bucket now has 1000 bytes (the maximum number of tokens available in
the conform bucket) and 200 bytes overflow the conform token bucket (because it only 200 bytes were
needed to fill the conform token bucket to capacity). These overflow bytes are placed in the exceed token
bucket, giving the exceed token bucket 300 bytes.
If the arriving packet is 1000 bytes, the packet conforms because enough bytes are available in the
conform token bucket. The conform action (transmit) is taken by the packet and 1000 bytes are removed
from the conform token bucket (leaving 0 bytes).
If the next packet arrives 0.20 seconds later, 200 bytes are added to the token bucket ((.20 * 8000)/8).
Therefore, the conform bucket now has 200 bytes. If the arriving packet is 400 bytes, the packet does not
conform because only 200 bytes are available in the conform bucket. Similarly, the packet does not
exceed because only 300 bytes are available in the exceed bucket. Therefore, the packet violates and the
violate action (drop) is taken.
Catalyst 4500 Series Switch Cisco IOS Command Reference—Release XE 3.9.xE and 15.2(5)Ex
2-548