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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 20 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 for Gigabit-capable Ethernet ports. On 10/100
Ethernet ports, all CoS values map to egress queue 1, which uses 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
Table 20-1 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 port trust states. It contains this
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
Step 1
configure terminal
Enter global configuration mode.
Step 2
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.
Step 3
flowcontrol receive off
flowcontrol send off
Disable flowcontrol on all interfaces.
Step 4
exit
Return to global configuration mode.
Step 5
mls qos
Enable QoS globally.
Step 6
end
Return to privileged EXEC mode.
Step 7
show mls qos
Verify your entries.
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.
