Configuring Low-Latency Queuing (LLQ)

Configuring Low-Latency Queuing (LLQ)

Figure 4-5 shows a flowchart showing the architecture of Low-Latency Queuing. The configuration that follows the diagram shows a specific example of configuring Low-Latency Queuing.

Figure 4-5. Low-Latency Queuing

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The tasks to configure Low-Latency Queuing are

STEP 1.	Define one or more class maps to specify traffic.
STEP 2.	Create a policy.
STEP 3.	Add class maps to the policy and specify one (or more) class(es) with priority bandwidth.
STEP 4.	Apply queuing policy to an interface.
STEP 5.	Verify policy configuration.

Step 1: Define One or More Class Maps to Specify Traffic

Router(config-cmap)# class-map match-any PRECEDENCE5	Creates class for precedence 5 traffic.
Router(config-cmap)# match precedence 5	Selects traffic with IP precedence 5.
Router(config-cmap)# class-map match-any PRECEDENCE7	Creates class for precedence 7 traffic.
Router(config-cmap)# match precedence 7	Selects traffic with IP precedence 7.
Router(config-cmap)# class-map match-any PRECEDENCE3	Creates class for precedence 3 traffic.
Router(config-cmap)# match precedence 3	Selects traffic with IP precedence 3.
Router(config-cmap)# class-map match-any PRECEDENCE0	Creates class for precedence 0 traffic.
Router(config-cmap)# match precedence 0	Selects traffic with IP precedence 0.
Router(config-cmap)# exit	Exit class-map configuration mode.

Step 2: Create a Policy

Router(config)# policy-map LETSQOSEM	Creates policy LETSQOSEM.

Step 3: Add Class Maps to the Policy and Specify One (or More) Class(es) with Priority Bandwidth

Router(config-pmap)# class PRECEDENCE5	Associates class PRECEDENCE5 with policy LETSQOSEM.
Router(config-pmap-c)# priority percent 10	Guarantees 10% bandwidth with first priority data handling.
Router(config-pmap-c)# class PRECEDENCE7	Associates class PRECEDENCE7 with policy LETSQOSEM.
Router(config-pmap-c)# bandwidth percent 15	Sets guaranteed bandwidth to 15 percent.
Router(config-pmap-c)# class PRECEDENCE3	Associates class PRECEDENCE3 with policy LETSQOSEM.
Router(config-pmap-c)# bandwidth percent 30	Sets guaranteed bandwidth to 30 percent.
Router(config-pmap-c)# class PRECEDENCE0	Associates class PRECEDENCE0 with policy LETSQOSEM.
Router(config-pmap-c)# bandwidth percent 20	Sets guaranteed bandwidth to 20 percent.
Router(config-pmap-c)# class class-default	Associates class class-default with policy LETSQOSEM for unspecified traffic.
Router(config-pmap-c)# fair-queue 20	Specifies the number of reserved dynamic queues for unclassified traffic.
Router(config-pmap-c)# exit	Returns to config-pmap mode.
Router(config-pmap)# exit	Returns to global configuration mode.

Step 4: Apply Queuing Policy to an Interface

Router(config)# interface FastEthernet 0/0	Chooses an interface to apply queuing policy.
Router(config-if)# service-policy output LETSQOSEM	Applies the queuing policy to outbound traffic.

Step 5: Verify Policy Configuration

Router# show policy-map interface fastethernet 0/0	Displays the configurations and statistics of policy maps applied at fastethernet 0/0.