enabled.

The show auto qos interface command can also be used with Frame Relay DLCIs and ATM PVCs.

Step 3 Display the data collected during the Auto Discovery phase:

• To display the packet statistics of all classes that are configured for all service policies either on the specified interface or subinterface or on a specific PVC on the interface, use the show policy-map interface command as shown in Figure .
• The counters displayed after you enter the show policy-map interface command are updated only if there is congestion on the interface. The command will also display policy information about Frame Relay PVCs, but only if Frame Relay traffic shaping (FRTS) is also enabled on the interface (manually or by Cisco AutoQoS).

Monitoring Cisco AutoQoS on Switches
Follow these three steps to monitor Cisco AutoQoS on Cisco Catalyst switches: Step 1 Examine Cisco AutoQoS templates and initial configuration:

• Use the show auto qos command to display the initial Cisco AutoQoS VoIP configuration on the switch. Figure shows the command syntax and an example. To display any user changes to that configuration, use the show running-config command. The show auto qos and the show running-config command output can be compared to identify the additional user-defined QoS settings. From the show command output, you can see that the switch has four output WRR queues available with weights 20, 1, 80 and 0 for queues 1, 2, 3, and 4 respectively. The wrr-queue cos command shows the CoS mapping for each queue as follows (the first number is the queue ID, the second one is the threshold id, the other numbers are CoS values).
  • Queue 4 is used for high-priority traffic (a value of 0 within the wrr-queue bandwidth command and a mapping of CoS 5 to queue 4 using the wrr-queue cos-map command).
  • Queue 2 is not used at all (a value of 1 within the wrr-queue bandwidth command and no mapping of CoS to queue 2 using the wrr-queue cos-map command).
  • Queue 1 gets 20 percent of any bandwidth not being used by Queue 4 and provides CoS 0, 1, 2, and 4.
  • Queue 3 gets 80 percent of any bandwidth not being used by Queue 4 and provides CoS 3, 6, and 7.
  • The CoS to DSCP mapping is shown, as is the trusted IP phone connection.

Step 2 Explore interface-level autogenerated QoS parameters:

• Use the show mls qos interface command as shown in Figure to display QoS information on the Cisco Catalyst switch at the interface level, including the configuration of the egress queues and the CoS-to-egress-queue maps, the interfaces that have configured policers, and ingress and egress statistics (including the number of bytes dropped).
• If no keyword is specified with the show mls qos interface command, the port QoS mode (DSCP trusted, CoS trusted, untrusted, and so forth), default CoS value, DSCP-to-DSCP-mutation map (if any) that is attached to the port, and policy map (if any) that is attached to the interface are displayed. If a particular interface is not specified, the information for all interfaces is displayed.

Step 3 Examine CoS-to-DSCP maps:

• Use the show mls qos maps command, as shown in Figure to display the current DSCP and CoS mappings. All the maps are globally defined.
• The cos-dscp keyword presents the default CoS-to-DSCP map. The supported CoS values are 0–7.
• The dscp-cos keyword presents the default DSCP-to-CoS mapping. The supported DSCP values are 0, 8, 10, 16, 18, 24, 26, 32, 34, 40, 46, 48, and 56.
• After a default map is applied, you can define the CoS-to-DSCP or DSCP-to-CoS map by entering consecutive mls qos map commands.

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Content 5.2 Mitigating Common Cisco AutoQoS Issues 5.2.1 Automation with Cisco AutoQoS Figure lists key QoS requirements of typical enterprises. Cisco AutoQoS automates QoS deployment for the most common enterprise scenarios and enables several Cisco IOS QoS mechanisms to meet the QoS requirements of various applications and traffic types discovered in the enterprise network. Enterprise requirements include the following:

• Identify trust boundary and extended trust boundary and protocols of interest.
• Determine the number of differentiated services (DiffServ) classes that will be defined for the enterprise network.
• Re-mark traffic based on local policy requirements.
• Determine the queuing methods that should be enabled.
• Define the individual class bandwidth needed to fulfill real-time traffic requirements and provide minimum bandwidth guarantees for other applications.
• Define transport-specific QoS features (traffic shaping, Multilink PPP [MLP], and transmit ring [tx-ring] settings).
• For low-bandwidth links (less than 768 kbps), specify necessary QoS features (compressed Real-Time Transport Protocol [cRTP], MLP link fragmentation and interleaving [LFI], or Frame Relay Fragmentation [FRF.12]).
• Define the alarm and event settings for monitoring purposes.

In addition, in a LAN environment, Cisco AutoQoS also has these requirements:

• Determine class of service (CoS)-to-differentiated services code point (DSCP) and IP precedence-to-DSCP mappings.
• Map CoS values to different egress queues (via CoS-to-DSCP maps).
• Set the queue sizes and weighted round robin (WRR) weights (that is, the appropriate WRR settings for Fast Ethernet interfaces versus Gigabit Ethernet interfaces).

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Content 5.2 Mitigating Common Cisco AutoQoS Issues 5.2.2 DiffServ QoS Mechanisms Enabled by Cisco AutoQoS Using Cisco best-practices recommendations, Cisco AutoQoS enables several QoS mechanisms to ensure optimal performance of autodiscovered enterprise applications. Cisco AutoQoS automatically provisions six QoS mechanisms using DiffServ technology as shown in Figure and described in detail below. Classification
Packet classification provides the ability to partition network traffic into multiple priority levels or classes of service. For example, by using the Internet Engineering Task Force (IETF)-defined DSCP values specified in DiffServ standards RFC 2474 and 2475, networks can categorize application traffic into a maximum of 64 traffic classes. Cisco AutoQoS defines up to 10 classes. When packets are classified, use the various QoS features in Cisco IOS software to assign the appropriate traffic-handling policies for each traffic class. Cisco AutoQoS either reuses the classification based on DSCP or IP precedence and CoS from the adjacent device (for example, the router or switch closer to the network edge) in trusted mode or activates Cisco Network-Based Application Recognition (NBAR) to classify the traffic on an ingress interface in untrusted mode. In either case, Cisco AutoQoS defines classes using the Cisco Modular QoS CLI (MQC) class maps. Marking
Marking tools mark a packet or flow with a specific priority. This marking is performed at a trust boundary. Classification and marking should take place at the network edge, typically in the wiring closet switches, within the Cisco IP phones themselves, or at voice endpoints. Packets can be marked as important by using Layer 2 CoS settings in the user priority bits of the 802.1p portion of the 802.1Q header or the IP precedence or DSCP bits in the type of service (ToS) byte of the IP version 4 (IPv4) header. For example, all Cisco IP phone Real-Time Transport Protocol (RTP) packets should be tagged with either of these values:

• CoS value of 5 for the Layer 2 802.1p settings and a DSCP value of expedited forwarding (EF)
• IP precedence value of 5
• Additionally, all control packets should be tagged with a Layer 2 CoS value of 3 and a Layer 3 DSCP value of 24–31 (or IP precedence value