31-11
Catalyst 2928 Switch Software Configuration Guide
OL-23389-01
Chapter 31 Configuring QoS
Configuring Standard QoS
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
“Configuring the CoS Value for an
Interface” section on page 31-11
.
Configuring the CoS Value for an Interface
QoS assigns the CoS value specified with the
mls qos cos
interface configuration command to untagged
frames received on trusted and untrusted ports.
Beginning in privileged EXEC mode, follow these steps to define the default CoS value of a port or to
assign the default CoS to all incoming packets on the port:
To return to the default setting, use the
no mls qos cos
{
default-cos
|
override
} interface configuration
command.
Enabling DSCP Transparency Mode
The switch supports the Differentiated Services Code Point (DSCP) transparency feature. It affects only
the DSCP field of a packet at egress. By default, DSCP transparency is disabled. The switch modifies
the DSCP field in an incoming packet, and the DSCP field in the outgoing packet is based on the QoS
configuration, including the port trust setting, policing and marking, and the DSCP-to-DSCP mutation
map.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface
interface-id
Specify the port to be configured, and enter interface configuration mode.
Valid interfaces include physical ports.
Step 3
mls qos cos
{
default-cos
|
override
}
Configure the default CoS value for the port.
•
For
default-cos,
specify a default CoS value to be assigned to a port. If
the packet is untagged, the default CoS value becomes the packet CoS
value. The CoS range is 0 to 7. The default is 0.
•
Use the
override
keyword to override the previously configured trust
state of the incoming packet and to apply the default port CoS value to
the port on all incoming packets. By default, CoS override is disabled.
Use the
override
keyword when all incoming packets on specified ports
deserve higher or lower priority than packets entering from other ports.
Even if a port was previously set to trust CoS or IP precedence, this
command overrides the previously configured trust state, and all the
incoming CoS values are assigned the default CoS value configured
with this
command. If an incoming packet is tagged, the CoS value of
the packet is modified with the default CoS of the port at the ingress
port.
Step 4
end
Return to privileged EXEC mode.
Step 5
show mls qos interface
Verify your entries.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
