37-22
Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 37 Configuring Quality of Service
Configuring QoS on Supervisor Engines II-Plus, II+10GE, IV, V, V-10GE, 4924, 4948, and 4948-10GE
Note On a given port, the Cisco IP phone discovery information is not maintained on the standby supervisor
engine. When the standby supervisor engine becomes active, it rediscovers the Cisco IP phone through
CDP. For a short time, the port are not in the trust state after the SSO switchover.
To enable trusted boundary on a port, perform this task:
To disable the trusted boundary feature, use the no qos trust device cisco-phone interface configuration
command.
Enabling Dynamic Buffer Limiting
Note Supervisor Engine 6-E, Supervisor Engine 6L-E, Catalyst 4900M, and Catalyst 4948E support DBL
using the MQC CLI, but not with the older QoS DBL CLI.
Dynamic buffer limiting (DBL) provides active queue management on Catalyst 4500 platforms. Refer to
“Active Queue Management” section on page 37-14 for details.
Through selective DBL, you can select the flows that are subjected to the DBL algorithm. You can enable
DBL globally on specific IP DSCP values or on specific CoS values.
This section includes the following topics:
• Enabling DBL Globally, page 37-23
• Selectively Enable DBL, page 37-23
Command Purpose
Step 1 Switch# configure terminal Enters global configuration mode.
Step 2 Switch(config)# interface
interface-id Enters interface configuration mode, and specifies the interface connected
to the Cisco IP phone.
Valid interfaces include physical interfaces.
Step 3 Switch(config)# qos trust [cos |
dscp]Configures the interface to trust the CoS value in received traffic. By
default, the port is not trusted.
Step 4 Switch(config)# qos trust device
cisco-phone Specifies 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.
Step 5 Switch(config)# end Returns to privileged EXEC mode.
Step 6 Switch# show qos interface
interface-id Verifies your entries.
Step 7 Switch# copy running-config
startup-config (Optional) Saves your entries in the configuration file.