Cisco 2950G 24 Software Configuration Guide - Page 533
Enabling Pass-Through Mode, Port Configuration, When a Cisco IP Phone is Present, Command, Purpose
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Chapter 26 Configuring QoS Configuring QoS Table 26-2 Port Configurations When Trusted Boundary is Enabled Port Configuration When a Cisco IP Phone is Present When a Cisco IP Phone is Absent The port trusts the CoS value The packet CoS value is trusted. The packet CoS value is assigned of the incoming packet. the default CoS value. The port trusts the DSCP The packet DSCP value is trusted. For tagged non-IP packets, the value of the incoming packet. packet CoS value is set to 0. For untagged non-IP packets, the packet CoS value is assigned the default CoS value. The port assigns the default CoS value to incoming packets. The packet CoS value is assigned The packet CoS value is assigned the default CoS value. the default CoS value. Enabling Pass-Through Mode In software releases earlier than Release 12.1(11)EA1, the switch is in pass-through mode. It uses the CoS value of incoming packets without modifying the DSCP value and sends the packets from one of the four egress queues. You cannot enable or disable pass-through mode if your switch is running a software release earlier than Release 12.1(11)EA1. In Release 12.1(11)EA1 or later, the switch assigns a CoS value of 0 to all incoming packets without modifying the packets. The switch offers best-effort service to each packet regardless of the packet contents or size and sends it from a single egress queue. Beginning in privileged EXEC mode, follow these steps to enable pass-through mode: Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Command Purpose configure terminal Enter global configuration mode. interface interface-id Enter interface configuration mode, and specify the interface on which pass-through mode is enabled. Valid interfaces include physical interfaces. mls qos trust cos pass-through dscp Enable pass-through mode. The interface is configured to trust the CoS value of the incoming packets and to send them without modifying the DSCP value. end Return to privileged EXEC mode. show mls qos interface [interface-id] Verify your entries. copy running-config startup-config (Optional) Save your entries in the configuration file. To disable pass-through mode, use the no mls qos trust pass-through dscp interface configuration command. If you enter the mls qos cos override and the mls qos trust [cos | dscp] interface commands when pass-through mode is enabled, pass-through mode is disabled. If you enter the mls qos trust cos pass-through dscp interface configuration command when the mls qos cos override and the mls qos trust [cos | dscp] interface commands are already configured, pass-through mode is disabled. 78-14982-01 Catalyst 2950 Desktop Switch Software Configuration Guide 26-15