Implementing QoS Using AutoQoS
The main advantage of using AutoQoS is that it simplifies the QoS configuration. If you lack the in-depth knowledge of QoS commands, AutoQoS can be used to implement QoS features consistently and accurately. After using AutoQoS, you can modify the configuration by using the MQC.
Before you enable AutoQoS on an interface, the following must be completed:
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Cisco Express Forwarding (CEF) should be enabled. CEF is a prerequisite for Network-Based Application Recognition (NBAR).
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NBAR should be enabled. AutoQoS for the Enterprise uses NBAR for traffic discovery and classification. AutoQoS VoIP does not.
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The correct bandwidth on the interface should be configured. AutoQoS will configure Low Latency Queueing (LLQ), Compressed Real-Time Protocol (cRTP), and Link Fragmentation and Interleaving (LFI) based on interface type and bandwidth.
| Router(config)# ip cef | Enables CEF on the router. |
| Router(config)# interface serial 0/0/0 | Moves to interface configuration mode. |
| Router(config-if)# bandwidth 512 | Sets bandwidth to 512 Kbps for accounting and cost calculation purposes. |
| Router(config-if)# ip address 192.168.1.1 255.255.255.252 | Assigns IP address and netmask to interface. |
| Router(config-if)# auto qos voip | Enables AutoQoS VoIP on this interface. |
Note
The command auto qos voip is from the first generation of AutoQoS. This command is used to automate the generation of QoS commands to prepare the device for VoIP traffic. The second generation is known as "AutoQoS for the Enterprise" and the command auto discovery qos must first be entered so that the router will discover and analyze network traffic. This discovery and analysis is done using NBAR. After the auto discovery qos command is entered, the command auto qos must be entered. This will allow for the creation of class maps based on the results of the discovery, and finally the creation and application of policy maps on the interface.