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Catalyst 2960 Switch SoftwareConfiguration Guide
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Chapter29 Co nfiguring QoS
Configuring Standard QoS
With the trusted setting, you also can use the trusted boundary feature t o prevent misuse of a
high-priority queue if a user bypasses the telephone and connects the PC directly to the switch. Without
trusted boundary, the CoS labels generated by the PC are trusted by the switch (because of the trus ted
CoS setting). By contrast, trusted boundary uses CDP to detect the pr esence of a Cisco IP Phone (such
as the Cisco IP Phone 7910, 7935, 7940, and 7960) on a switch port. If the telephone is not detected, the
trusted boundary feature disables the trusted setting on the switch port and prevents misuse of a
high-priority queue. Note that the trusted boundary feature is not effective if the PC and Cisco IP Phone
are connected to a hub that is connected to the switch.
In some situations, you can prevent a PC connected to the Cisco IP Ph one from taking advantage of a
high-priority data queue. You can use the switchport priority extend cos interface configuration
command to configure the telephone through the switch CLI to override the priority of the traffic
received from the PC.
Beginning in privileged EXEC mode, follow these steps to enable trusted bound ary on a port:
To disable the trusted boundary feature, use the no mls qos trust device interface configuration
command.
Enabling DSCP Transparency Mode
The switch supports the 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 qua lity of service (QoS) configuration,
including the port trust setting, policing and marking, and the DSCP-to-DSCP mutation map.
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 cdp run Enable CDP globally. By default, CDP is enabled.
Step3 interface interface-id Specify the port connected to the Cisco IP Phone, and enter interface
configuration mode.
Valid interfaces include physical ports.
Step4 cdp enable Enable CDP on the port. By default, CDP is enabled.
Step5 mls qos trust cos
mls qos trust dscp
Configure the switch port to trust the CoS value in traffic received from the
Cisco IP Phone.
or
Configure the routed port to trust the DSCP value in traffic received from
the Cisco IP Phone.
By default, the port is not trusted.
Step6 mls qos trust device cisco-phone Specify that the Cisco IP Phone is a trusted device.
You cannot enable both trusted boundary and auto-QoS (auto qos voip
interface configuration command) at the same time; they are mutually
exclusive.
Step7 end Return to privileged EXEC mode.
Step8 show mls qos interface Verify your entries.
Step9 copy running-config startup-config (Optional) Save your entries in the configuration file.