Chapter 7: Implementing AutoQoS
AutoQoS VOIP:
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First generation of AutoQoS
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Available on routers and switches
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Relies on NBAR for classification and marking
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Configures QoS for VOIP traffic only
AutoQoS Enterprise:
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Second generation, introduced in IOS 12.3(7)T
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Available only on routers
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Two deployment stages: traffic discovery via NBAR, and policy implementation
AutoQoS interface requirements:
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CEF must be enabled for the interface
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No service policy can already be applied
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Bandwidth must be accurately configured
Deploying AutoQoS Enterprise on Routers
The default AutoQoS discovery period is three days, but this can be modified.
AutoQoS discovery is enabled with auto discovery qos [trust] on an interface.
Discovery results (even unfinished) can be viewed with show auto discovery qos.
After the discovery phase has completed, AutoQoS is enabled per interface:
Router(config-if)# auto qos [voip [trust] [fr-atm]]
The voip keyword forces legacy AutoQoS (VOIP only).
Verification:
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show auto qos - Displays the auto-generated AutoQoS class and policy maps
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show policy-map interface - Displays applied policy map and QoS parameters for each interface
Deploying AutoQoS VOIP on Switches
To configure a port as trusted only when a trusted device is detected, such as a Cisco IP phone (requires CDPv2):
Switch(config-if)# auto qos voip cisco-phone
To enable a permanently trusted interface (for example, a trunk or uplink):
Switch(config-if)# auto qos voip trust
The default CoS-to-DSCP mappings can be modified with mls qos map.
Verification:
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show auto qos - Displays the auto-generated AutoQoS configuration
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show mls qos interface <interface> - Displays QoS parameters for an interface
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show mls qos maps - Displays the CoS-to-DSCP mappings used by AutoQoS
Common AutoQoS Issues
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Too many classes are created
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The configuration generated by AutoQoS doesn't automatically adjust to changing network conditions
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Even with auto discovery, AutoQoS may not fit some scenarios