Cisco WS-C3550-12G Software Configuration Manual page 475

Chapter 20 Configuring QoS
Beginning in privileged EXEC mode, follow these steps to configure the port to trust the classification
of the traffic that it receives:
Command
Step 1 configure terminal
Step 2
mls qos
Step 3
interface interface-id
Step 4 mls qos trust {cos | dscp | ip-precedence}
Step 5
end
Step 6 show mls qos interface
Step 7 copy running-config startup-config
To return a port to its untrusted state, use the no mls qos trust interface configuration command.
For information on how to change the default CoS value, see the
Interface" section on page
"Configuring the CoS-to-DSCP Map" section on page
78-11194-03
Purpose
Enter global configuration mode.
Enable QoS globally.
Enter interface configuration mode, and specify the interface to be
trusted.
Valid interfaces include physical interfaces.
Configure the port trust state.
By default, the port is not trusted.
The keywords have these meanings:
• cos—Classifies ingress packets with the packet CoS values. For
untagged packets, the port default CoS value is used. The default
port CoS value is 0.
dscp—Classifies ingress packets with packet DSCP values. For
•
non-IP packets, the packet CoS value is used if the packet is
tagged; for untagged packets, the default port CoS is used.
Internally, the switch maps the CoS value to a DSCP value by
using the CoS-to-DSCP map.
ip-precedence—Classifies ingress packets with the packet
•
IP-precedence values. For non-IP packets, the packet CoS value
is used if the packet is tagged; for untagged packets, the default
port CoS is used. Internally, the switch maps the CoS value to a
DSCP value by using the CoS-to-DSCP map.
Use the cos keyword setting if your network is composed of Ethernet
LANs, Catalyst 3500 XL and 2900 XL switches, and has no more
than two types of traffic. Recall that on Catalyst 3500 XL and 2900
XL switches, CoS configures each transmit port with a
normal-priority transmit queue and a high-priority transmit queue.
Use the dscp or ip-precedence keyword if your network is not
composed of only Ethernet LANs and if you are familiar with
sophisticated QoS features and implementations.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
20-24. For information on how to configure the CoS-to-DSCP map, see the
Catalyst 3550 Multilayer Switch Software Configuration Guide
"Configuring the CoS Value for an
20-39.
Configuring QoS
20-23