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Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
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Chapter 52 Configuring QoS
Configuring QoS on the Switch
Configuring the Trust State of a Port
This command configures the trust state of a port (for more information, see the “Ethernet Ingress Port
Marking, Scheduling, Congestion Avoidance, and Classification” section on page 52-12). By default, all
ports are untrusted.
To configure the trust state of a port, perform this task in privileged mode:
Note the following syntax guidelines when configuring the trust state of a port:
• The trust-ipprec and trust-dscp keywords are supported only with a Layer 3 switching engine.
• 1q4t ports (except Gigabit Ethernet) do not support the trust-ipprec and trust-dscp port keywords.
You must configure a trust-ipprec or trust-dscp ACL that matches the ingress traffic to apply the
trust-ipprec or trust-dscp trust state.
• On the 1q4t ports (except Gigabit Ethernet), the trust-cos port keyword displays an error message,
activates the receive-queue drop thresholds, and—as indicated by the error message—does not apply
the trust-cos trust state to the traffic. You must configure a trust-cos ACL that matches the ingress
traffic to apply the trust-cos trust state.
This example shows how to configure port 1/1 with the trust-cos keyword:
Console> (enable) set port qos 1/1 trust trust-cos
Port 1/1 qos set to trust-cos
Console> (enable)
Note Only the ISL or 802.1Q frames carry the CoS values. Configure the ports with the trust-cos keyword
only when the received traffic is ISL or 802.1Q frames carrying the CoS values that you know to be
consistent with the network policy.
Configuring the CoS Value for a Port
Note Whether or not QoS uses the CoS value that is applied with the set port qos ...cos command depends on
the trust state of the port and the trust state of the traffic that is received through the port. The
set port qos ... cos command does not configure the trust state of the port or the trust state of the traffic that
is received through the port. To use the CoS value that is applied with the
set port qos ... cos command,
configure a trust-CoS ACL that matches the ingress traffic; or for a port that receives no tagged traffic,
configure the port to trust CoS.
The unmarked frames from the ports that are configured as trusted and all frames from the ports that are
configured as untrusted are assigned the CoS value that is specified with this command.
Task Command
Step 1
Configure the trust state of a port. set port qos trust {untrusted | trust-cos |
trust-ipprec | trust-dscp}
Step 2
Verify the configuration. show port qos
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