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Configuring The Cos Value For An Interface; Configuring A Trusted Boundary To Ensure Port Security - Cisco WS-C2960-24LC-S Software Configuration Manual

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Configuring Standard QoS

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:
Command
Step 1
configure terminal
Step 2
interface interface-id
Step 3
mls qos cos {default-cos | override}
Step 4
end
Step 5
show mls qos interface
Step 6
copy running-config startup-config
To return to the default setting, use the no mls qos cos {default-cos | override} interface configuration
command.

Configuring a Trusted Boundary to Ensure Port Security

In a typical network, you connect a Cisco IP Phone to a switch port, as shown in
page
IP Phone guarantees the voice quality through a shared data link by marking the CoS level of the voice
packets as high priority (CoS = 5) and by marking the data packets as low priority (CoS = 0). Traffic
sent from the telephone to the switch is typically marked with a tag that uses the IEEE 802.1Q header.
The header contains the VLAN information and the class of service (CoS) 3-bit field, which is the
priority of the packet.
For most Cisco IP Phone configurations, the traffic sent from the telephone to the switch should be
trusted to ensure that voice traffic is properly prioritized over other types of traffic in the network. By
using the mls qos trust cos interface configuration command, you configure the switch port to which
Catalyst 2960 Switch Software Configuration Guide
28-36
Purpose
Enter global configuration mode.
Specify the port to be configured, and enter interface configuration mode.
Valid interfaces include physical ports.
Configure the default CoS value for the port.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
28-34, and cascade devices that generate data packets from the back of the telephone. The Cisco
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 DSCP, 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.
Chapter 28
Configuring QoS
Figure 28-11 on
OL-8603-04

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