30-24
Catalyst2950 and Catalyst2955 Switch Software Configuration Guide
78-11380-10
Chapter30 Co nf iguring QoS
Configuring Standard QoS
With the trusted setting, you also can use the trusted boundary feature t o prevent misuse o f 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 esenc e of a Ci sco I P Pho ne (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 f ro m ta king advantage o f 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 prior ity o f th e tra ffic
received from the PC.
Beginning in privileged EXEC mode, follow these steps to configure trusted boundary on a switch port:
When you enter the no mls qos trust interface configuration command, trusted boundary is not disabled.
If this command is entered and the port is connected to a Cisco IP Phone, the port does not trust the
classification of traffic that it receives. To disable trusted boundary, use the no mls qos trust device
interface configuration command
If you enter the mls qos cos override interface configuration command, the port does not trust the
classification of the traffic that it receives, even when it is connected to a Cisco IP Phone.
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 cdp enable Enable CDP globally. By default, it is enabled.
Step3 interface interface-id Specify the interface to be trusted, and enter interface configuration
mode.
Valid interfaces include physical interfaces.
Step4 cdp enable Enable CDP on the interface. By default, CDP is enabled.
Step5 mls qos trust device cisco-phone Configure the Cisco IP Phone as a trusted device on the interface.
You cannot enable both trusted boundary and auto-QoS (auto qos
voip interface configuration command) at the same time; they are
mutually exclusive.
Step6 mls qos trust cos Configure the port trust state to trust the CoS value of the ingress
packet.
By default, the port is not trusted.
Note In software releases earlier than Cisco IOS
Release 12.1(11)EA1, the mls qos trust cos command is
available only when the switch is running the EI.
For more information on this command, refer to the command
reference for this release.
Step7 end Return to privileged EXEC mode.
Step8 show mls qos interface [interface-id]
[policers]Verify your entries.
Step9 copy running-config startup-config (Optional) Save your entries in the configuration file.