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Quality of Service: Managing Bandwidth More Effectively
Advanced Classifier-Based QoS
Override of Global QoS Settings
After you apply a QoS policy to an interface, the classifier-based settings
configured by QoS actions in the policy override any 802.1p CoS or DSCP
codepoint values that were globally-configured on the switch to mark packets
using the QoS commands described in “Globally-Configured QoS” on page
6-19.
If you use a classifier-based QoS configuration along with globally-configured
QoS commands, the order of precedence in which 802.1p priority, IP prece-
dence, and DSCP settings mark selected packets is as follows, from highest
(1) to lowest (9):
Table 6-10. Order of Precedence for Classifier-Based QoS over Global QoS
Precedence
Order
QoS Feature Reference
1 Classifier-based port-specific policy Page 6-71
2 Classifier-based VLAN-specific policy Page 6-71
3 Globally-configured TCP/UDP priority Page 6-24
4 Globally-configured IP-device priority Page 6-33
5 Globally-configured IP Type-of-Service priority Page 6-41
6 Globally-configured Layer 3-Protocol priority Page 6-54
7 Globally-configured VLAN-ID priority Page 6-56
8 Globally-configured Source-Port priority Page 6-62
9 802.1p CoS in Layer 2 VLAN header
1
Page 6-12
1
In a tagged VLAN environment, the incoming 802.1p priority is used as the default QoS
classifier to determine how a packet is handled if no global or classifier-based QoS match
criterion with a higher precedence matches.
Viewing a Classifier-Based QoS Configuration
Use the following show commands to display information about a classifier-
based QoS configuration and statistics or resource usage on QoS policies.
Syntax: show class < class-name >
Displays a traffic-class configuration, including all match/
ignore statements used to classify packets.
6-81