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39-36

Catalyst 3750-X and 3560-X Switch Software Configuration Guide

OL-21521-01

Chapter 39 Configuring QoS

Configuring Standard QoS

Default Mapping Table Configuration

Table 39-12 on page 39-70 shows the default CoS-to-DSCP map.

Table 39-13 on page 39-71 sho

ws the default IP-precedence-to-DSCP map.

Table 39-14 on page 39-73 sho

ws the default DSCP-to-CoS map.

The default DSCP-to-DSCP-mutation map is a null map, which maps an incoming DSCP value to the

same DSCP v

alue.

The default policed-DSCP map is a null map, which maps an incoming DSCP value to the same DSCP

alue (no markdown).

Standard QoS Configuration Guidelines

Before beginning the QoS configuration, you should be aware of this information in these sections:

• “QoS ACL Guidelines” section on page 39-36

• “IPv6 QoS ACL Guidelines” section on page 39-36

• “Applying QoS on Interfaces” section on page 39-37

• “Configuring IPv6 QoS on Switch Stacks” section on page 39-37

• “Policing Guidelines” section on page 39-38

• “General QoS Guidelines” section on page 39-38

QoS ACL Guidelines

These are the guidelines with for configuring QoS with access control lists (ACLs):

• It is not possible to match IP fragments against configured IP extended ACLs to enforce QoS. IP

fragments are sent as best-effort. IP fragments are denoted by fields in the IP header.

• Only one ACL per class map and only one match class-map configuration command per class map

are supported. The ACL can have multiple ACEs, which match fields against the contents of the

packet.

• A trust statement in a policy map requires multiple hardware entries per ACL line. If an input service

policy map contains a trust statement in an ACL, the access list might be too large to fit into the

available QoS hardware memory, and an error can occur when you apply the policy map to a port.

Whenever possible, you should minimize the number of lines is a QoS ACL.

IPv6 QoS ACL Guidelines

See Understanding IPv6 ACLs, page 38-2.

Note IPv6 QoS ACLs are not supported on switches running the LAN base feature set.

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