Cisco Systems ME 3400 Input and Output Policies

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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide

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Chapter 33 Configuring QoS

Understanding QoS

class1 interface configuration command attaches all the characteristics of the traffic policy named class1

to the specified interface. All packets leaving the specified interface are evaluated according to the

criteria specified in the traffic policy named class1.

Input and Output Policies

Policy maps are either input policy maps or output policy maps, attached to packets as they enter or leave

the switch by service policies applied to interfaces. Input policy maps perform policing and marking on

received traffic. Policed packets can be dropped or reduced in priority (marked down) if they exceed th e

maximum permitted rates. Output policy maps perform scheduling and queuing on traffic as it leaves the

switch.

Input policies and output policies have the same basic structure; the difference is in the characteristics

they regulate. Figure 33-2 shows the relationship of input and output policies.

You can configure a maximum of 256 policy maps. You can apply one input policy map and one output

policy map to an interface.

Figure 33-2 Input and Output Policy Relationship

Input Policy Maps

Input policy map classification criteria include matching a CoS, a DSCP, or an IP precedence value or

matching an access control list (ACL) or VLAN ID (for per-port, per-VLAN QoS). Input policy maps

can have any of these actions:

• Setting or marking a CoS, a DSCP, an IP precedence, or QoS group value

• Individual policing

• Aggregate policing

Only input policies provide matching on access groups or VLAN IDs, and only output policies provide

matching on QoS groups. You can assign a QoS group number in an input policy and match it in the

output policy. The class class-default is used in a policy map for any traffic that does not explicitly

match any other class in the policy map. Input policy maps do not support queuing and scheduling

keywords, such as bandwidth, queue-limit, priority, and shape average.

An input policy map can have a maximum of 32 classes, one of which is class-default. You can configure

a maximum of 31 classes in an input policy.

Ingress

port

Apply

input

policy

Apply

output

policy

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Switching

and

forwarding

Egress

port

Apply

output

policy

Apply

input

policy