20-21
Catalyst 3550 Multilayer Switch Software Configuration Guide
78-11194-03
Chapter20 Configuring QoS Configuring QoS
Enabling QoS Globally
By default, QoS is disabled on the switch, which means that the switch offers best-effort service to each
packet regardless of the packet contents or size. All CoS values map to egress queue 1 with both tail-drop
thresholds set to 100 percent of the total queue size f or Gi gabi t-c apab le Ethe rn et por ts. O n 10 /1 00
Ethernet ports, all CoS values map to egress queue 1, which use s minimum-reserve level 1 and can hold
up to 100 packets. When the buffer is full, packets are dropped.
Beginning in privileged EXEC mode, follow these steps to enable QoS:
After QoS is enabled, the default settings are as shown in Table20-1 on page 20-18.
To disable QoS, use the no mls qos global configuration command.
Configuring Classification Using Port Trust States
This section describes how to classify incoming traffic by using p ort t rust stat es. It c on tains t his
configuration information:
Configuring the Trust State on Ports within the QoS Domain, page 20-22
Configuring the CoS Value for an Interface, page 20-24
Configuring the DSCP Trust State on a Port Bordering Another QoS Domain, page 20-25
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 interface range port-range Enter interface configuration mode, and execute a command
on multiple interfaces.
You can define up to five interface ranges with a single
command, with each range separated by a comma.
All interfaces in a range must be the same type; that is, all Fast
Ethernet ports or all Gigabit Ethernet ports.
Step3 flowcontrol rece i ve o ff
flowcontrol send off
Disable flowcontrol on all interfaces.
Step4 exit Return to global configuration mode.
Step5 mls qos Enable QoS globally.
Step6 end Return to privileged EXEC mode.
Step7 show mls qos Verify your entries.
Step8 copy running-config startup-config (Optional) Save your entries in the configuration file.