Catalyst 6500 Release 12.2SY Software Configuration Guide

Prerequisites for Policy-Based Queueing
Restrictions for Policy-Based Queueing
Information About Policy-Based Queueing
- Port-Based Queue Types
- Queueing Policies
How to Configure Policy-Based Queueing
Configuration Examples for Policy-Based Queueing

Policy-Based Queueing

Note ● Queueing is optional. Use the commands described in this section to configure queueing on ports that serve congested links.

For complete syntax and usage information for the commands used in this chapter, see these publications:

http://www.cisco.com/en/US/products/ps9536/prod_command_reference_list.html

Cisco IOS Release 12.2SY supports only Ethernet interfaces. Cisco IOS Release 12.2SY does not support any WAN features or commands.

Tip For additional information about Cisco Catalyst 6500 Series Switches (including configuration examples and troubleshooting information), see the documents listed on this page:

http://www.cisco.com/en/US/products/hw/switches/ps708/tsd_products_support_series_home.html

Participate in the Technical Documentation Ideas forum

Prerequisites for Policy-Based Queueing

None.

Restrictions for Policy-Based Queueing

DSCP-based queueing is supported on 8q4t, 1p7q2t, and 1p7q4t ports. The Supervisor Engine 2T-10GE ports are 8q4t/1p7q4t with the platform qos 10g-only global configuration command configured, which disables the Gigabit Ethernet ports on the supervisor engine.

Note In releases where CSCts82932 is not resolved, do not use the default DSCP-based queue mapping for 8q4t ingress queues unless you configure supporting bandwidth and queue limits.

The presence of a match dscp command or a match precedence command in a class map that is used in a queueing policy attached to a port enables DSCP-based queueing on the port in the direction that the queueing policy is attached.
CoS-based queueing is always used for non-IP traffic, IP multicast traffic, and IP unknown unicast flood traffic.
Class maps that are used in queueing policies can contain any combination and number of match dscp, match precedence, or match cos commands.
You can attach one input and one output queueing policy to an interface, in addition to policies that configure marking or policing.
To support migration from Cisco IOS Release 12.2SX configurations, Cisco IOS Release 12.2SY supports global configuration mode and interface configuration mode queueing commands.

– When you attach an ingress or egress queueing policy to a port, all interface configuration mode queueing commands on the port are deleted.

– An attached ingress or egress queueing policy supercedes the effect of any configured global configuration mode queueing commands.

– If you attach a queueing policy in only one direction, the queueing configuration of the other direction is either the defaults or is defined by any configured global configuration mode queueing commands.

– You cannot configure any interface configuration mode queueing commands on a port that has a queueing policy attached.

Policy-based queueing is supported on all modules that Cisco IOS Release 12.2SY supports with the Supervisor Engine 2T-10GE.
Queueing policies are specific to particular port types because a queueing policy cannot contain any commands that are not supported by the port to which it will be attached (see the “Configuration Examples for Policy-Based Queueing” section). Commands not supported on a port are not ignored. You cannot successfully apply a policy with unsupported commands to a port.
For clarity, configure queueing policy names that correspond to the port type it supports; for example 1q2t_1q8t_ingress.
Queueing policies can contain multiple class maps; each class map configures a queue.
A policy-map class defined by a class command that uses a class map and that contains the policy-map class priority command configures the priority queue. (The priority queue is the highest-numbered queue.) The class-map filters the QoS values (CoS or DSCP) it is configured with to the priority queue.
Enabling SRR on a port disables the priority queue.
A policy-map class defined by a class command that uses a class map and that does not contain the policy-map class priority command configures the highest-numbered nonpriority queue. (If the port has a priority queue, the highest-numbered nonpriority queue is numbered one less than the priority queue. If the port does not have a priority queue, the highest-numbered queue is a nonpriority queue.) Subsequent such commands define the configuration of the remaining nonpriority queues in reverse numerical order. You cannot skip a queue, but configuration of all queues is not required. The class-map filters the QoS values it is configured with to the nonpriority queue being configured.
A class command that uses the class-default keywords configures queue 1. The class-default keywords filter all remaining QoS values to queue 1.
For each nonpriority queue, policy-map class queue-limit or random-detect commands assign QoS values (CoS or DSCP) to thresholds within a queue. Thresholds are configured in numerical order. You cannot skip a threshold, but configuration of all threshold is not required. QoS values that are to be applied to the thresholds must be from the group of values that the class-map filters to the queue.

– The first queue-limit or random-detect command assigns QoS values to the first threshold, and configures the percentage value applied to it.

– Subsequent queue-limit or random-detect commands that are configured with the same percentage value assign additional QoS values to the first threshold.

– The next queue-limit or random-detect command that is configured with a different percentage value assigns QoS values to the numerically next threshold, and configures the percentage value applied to it.

– Subsequent queue-limit or random-detect commands that are configured with the same percentage value assign additional QoS values to the numerically next threshold.

– Each queue-limit or random-detect command with a different percentage defines the next unconfigured threshold and any subsequent commands that repeat a percentage value assign additional QoS values to a configured threshold.

– All unconfigured thresholds are at 100%.

– All unassigned QoS labels are assigned to the highest-numbered threshold.

Information About Policy-Based Queueing

Port-Based Queue Types

Ingress and Egress Buffers and Queues

The Ethernet port ASICs have buffers that are divided into a fixed number of queues. When congestion avoidance is enabled, PFC QoS uses the traffic’s Layer 2 CoS value or, on some port types, the Layer 3 DSCP values, to assign traffic to the queues. The buffers and queues store frames temporarily as they transit the switch. PFC QoS allocates the port ASIC memory as buffers for each queue on each port.

The Ethernet ports support the following types of queues:

Nonpriority queues
Priority queues

The Ethernet ports support the following types of scheduling algorithms between queues:

Shaped round robin (SRR)—SRR allows a queue to use only the allocated bandwidth.
Deficit weighted round robin (DWRR)—DWRR keeps track of any lower-priority queue under-transmission caused by traffic in a higher-priority queue and compensates in the next round.
Weighted Round Robin (WRR)—WRR does not explicitly reserve bandwidth for the queues. Instead, the amount of bandwidth assigned to each queue is user configurable. The percentage or weight allocated to a queue defines the amount of bandwidth allocated to the queue.
Priority queueing—Strict priority queueing allows delay-sensitive data such as voice to be dequeued and sent before packets in other queues are dequeued, giving delay-sensitive data preferential treatment over other traffic. The switch services traffic in the strict-priority transmit queue before servicing the nonpriority queues. After transmitting a packet from a nonpriority queue, the switch checks for traffic in the strict-priority queue. If the switch detects traffic in the strict-priority queue, it suspends its service of the nonpriority queue and completes service of all traffic in the strict-priority queue before returning to the nonpriority queue.

The Ethernet ports provide congestion avoidance with these types of thresholds within a queue:

Weighted Random Early Detection (WRED)—On ports with WRED drop thresholds, frames with a given QoS label are admitted to the queue based on a random probability designed to avoid buffer congestion. The probability of a frame with a given QoS label being admitted to the queue or discarded depends on the weight and threshold assigned to that QoS label.

For example, if CoS 2 is assigned to queue 1, threshold 2, and the threshold 2 levels are 40 percent (low) and 80 percent (high), then frames with CoS 2 will not be dropped until queue 1 is at least 40 percent full. As the queue depth approaches 80 percent, frames with CoS 2 have an increasingly higher probability of being discarded rather than being admitted to the queue. Once the queue is over 80 percent full, all CoS 2 frames are dropped until the queue is less than 80 percent full. The frames the switch discards when the queue level is between the low and high thresholds are picked out at random, rather than on a per-flow basis or in a FIFO manner. This method works well with protocols such as TCP that can adjust to periodic packet drops by backing off and adjusting their transmission window size.

Tail-drop thresholds—On ports with tail-drop thresholds, frames with a given QoS label are admitted to the queue until the drop threshold associated with that QoS label is exceeded; subsequent frames of that QoS label are discarded until the threshold is no longer exceeded. For example, if CoS 1 is assigned to queue 1, threshold 2, and the threshold 2 watermark is 60 percent, then frames with CoS 1 will not be dropped until queue 1 is 60 percent full. All subsequent CoS 1 frames will be dropped until the queue is less than 60 percent full. With some port types, you can configure the nonpriority receive queue to use both a tail-drop and a WRED-drop threshold by mapping a CoS value to the queue or to the queue and a threshold. The switch uses the tail-drop threshold for traffic carrying CoS values mapped only to the queue. The switch uses WRED-drop thresholds for traffic carrying CoS values mapped to the queue and a threshold. All LAN ports of the same type use the same drop-threshold configuration.

Note ● You can enable DSCP-based queues and thresholds on 8q4t, 1p7q2t, and 1p7q4t ports (see the “Module to Queue Type Mappings” section), either in a queueing policy or with legacy interface commands (see the “Legacy Configuration Procedures for DSCP-Based Queue Mapping” section).

DSCP-based queueing is supported on 8q4t, 1p7q2t, and 1p7q4t ports. The Supervisor Engine 2T-10GE ports are 8q4t/1p7q4t with the platform qos 10g-only global configuration command configured. To configure DSCP-based queue mapping on Supervisor Engine 2T ports, you must enter shutdown interface configuration mode commands for the Supervisor Engine 2T Gigabit Ethernet ports, and then enter the platform qos 10g-only global configuration command, which disables the Gigabit Ethernet ports on the Supervisor Engine 2T.
In releases where CSCts82932 is not resolved, do not use the default DSCP-based queue mapping for 8q4t ingress queues unless you configure supporting bandwidth and queue limits.

The switch provides congestion avoidance with the combination of multiple queues and the scheduling algorithms associated with each queue.

Ingress Queue Types

To see the queue structure of a LAN port, enter the show queueing interface type slot/port | include type command. The command displays one of the following architectures:

1q2t indicates one nonpriority queue with one configurable tail-drop threshold and one nonconfigurable tail-drop threshold.
2q4t indicates two nonpriority queues, each with four configurable tail-drop thresholds.
2q8t indicates two nonpriority queues, each with eight configurable tail-drop thresholds.
8q4t indicates eight nonpriority queues, each with four thresholds, each configurable as either WRED-drop or tail-drop, with support for DSCP-based queueing.

Note In releases where CSCts82932 is not resolved, do not use the default DSCP-based queue mapping for 8q4t ingress queues unless you configure supporting bandwidth and queue limits.

8q8t indicates eight nonpriority queues, each with eight thresholds, each configurable as either WRED-drop or tail-drop.
1p1q4t indicates:

– One strict-priority queue

– One nonpriority queue with four configurable tail-drop thresholds.

1p7q2t indicates the following:

– One strict-priority queue

– Seven nonpriority queues, each with two thresholds, each threshold configurable as either WRED-drop or tail-drop

– Supports DSCP-based queueing

Egress Queue Types

To see the queue structure of an egress LAN port, enter the show queueing interface type slot/port | include type command. The command displays one of the following architectures:

1p3q8t indicates the following:

– One strict-priority queue

– Three nonpriority queues, each with eight thresholds, each threshold configurable as either WRED-drop or tail-drop

1p7q4t indicates the following:

– One strict-priority queue

– Seven nonpriority queues, each with four thresholds, each threshold configurable as either WRED-drop or tail-drop

– Supports DSCP-based queueing

1p7q8t indicates the following:

– One strict-priority queue

– Seven nonpriority queues, each with eight thresholds, each threshold configurable as either WRED-drop or tail-drop

Module to Queue Type Mappings

Table 61-1 Supervisor Engine Module QoS Queue Structures
Supervisor Engines	Ingress Queue and Drop Thresholds	Ingress Queue Scheduler	Egress Queue and Drop Thresholds	Egress Queue Scheduler	Ingress Buffer Size	Egress Buffer Size
VS-S2T-10G-XL, VS-S2T-10G
With Gigabit Ethernet ports enabled	2q4t	WRR	1p3q4t	DWRR or SRR	128 MB	112 MB
With Gigabit Ethernet ports enabled	Does not support DSCP-based queueing.
With Gigabit Ethernet ports disabled	8q4t	WRR	1p7q4t	DWRR or SRR
With Gigabit Ethernet ports disabled	Supports DSCP-based queueing. In releases where CSCts82932 is not resolved, do not use the default DSCP-based queue mapping for 8q4t ingress queues unless you configure supporting bandwidth and queue limits.

Table 61-2 10-Gigabit Ethernet Modules
Modules	Ingress Queue and Drop Thresholds	Ingress Queue Scheduler	Egress Queue and Drop Thresholds	Egress Queue Scheduler	Total Buffer Size	Ingress Buffer Size	Egress Buffer Size
WS-X6908-10GE (supports DSCP-based queueing)	8q4t	DWRR	1p7q4t	DWRR SRR	200 MB	108 MB	90 MB
WS-X6908-10GE (supports DSCP-based queueing)	Note In releases where CSCts82932 is not resolved, do not use the default DSCP-based queue mapping for 8q4t ingress queues unless you configure supporting bandwidth and queue limits.
WS-X6816-10T-2T, WS-X6716-10T, WS-X6816-10G-2T, WS-X6716-10GE (supports DSCP-based queueing)
Performance mode	8q4t	DWRR	1p7q4t	DWRR SRR	198 MB	108 MB per port	90 MB per port
Performance mode	Note In releases where CSCts82932 is not resolved, do not use the default DSCP-based queue mapping for 8q4t ingress queues unless you configure supporting bandwidth and queue limits.
Oversubscription mode	1p7q2t	DWRR	1p7q4t	DWRR SRR	91 MB	90 MB per port	1 MB per port group
WS-X6704-10GE	8q8t	WRR	1p7q8t	DWRR	16 MB	2 MB	14 MB

Table 61-3 Gigabit and 10/100/1000 Ethernet Modules
Modules	Ingress Queue and Drop Thresholds	Ingress Queue Scheduler	Egress Queue and Drop Thresholds	Egress Queue Scheduler	Total Buffer Size	Ingress Buffer Size	Egress Buffer Size
WS-X6848-TX-2T, WS-X6748-GE-TX, WS-X6848-SFP-2T, WS-X6748-SFP, WS-X6824-SFP-2T, WS-X6724-SFP
	2q8t	WRR	1p3q8t	DWRR	1.3 MB	166 KB	1.2 MB

Queueing Policies

Queueing policies use class-maps with match commands (see Table 61-4 ) and policy maps with scheduling and congestion management commands (see Table 61-5 ).

Table 61-4 Queueing Policy Class Map match Commands and Match Criteria
match Commands	Match Criteria
match cos cos_list	CoS values.
match dscp dscp_list	DSCP values.
match precedence precedence_list	Precedence values.
Note The presence of a match dscp command or a match precedence command in a class map that is used in a queueing policy attached to a port configures DSCP-based queueing in the direction of the policy (ingress or egress) on that port. CoS-based queueing is always used for non-IP traffic, IP multicast traffic, and IP unknown unicast flood traffic. Class maps that are used in queueing policies can contain both match dscp commands and match cos commands.

Table 61-5 Queueing Policy-Map Class Commands
Queueing Commands	Description
bandwidth [remaining] percent percentage	Allocates bandwidth between nonpriority queues. The remaining keyword is required on ports that have a priority queue.
shape average percent percentage	Enables SRR, which allocates limited bandwidth between nonpriority egress queues (see “SRR” in the “Module to Queue Type Mappings” section).
priority	Applies a policy-map class to a priority queue.
queue-limit percent percent_of_total_buffer_size	Sets the queue size.
queue-limit multiple-type-based	Enables application of CoS, precedence, and DSCP values to a tail-drop threshold.
queue-limit cos cos_value percent percent_of_qsize	Applies one CoS value to a tail-drop threshold and configures the threshold percentage.
queue-limit dscp dscp_value percent percent_of_qsize	Applies one DSCP value to a tail-drop threshold and configures the threshold percentage.
queue-limit precedence precedence_value percent percent_of_qsize	Applies one precedence value to a tail-drop threshold and configures the threshold percentage.
queue-limit cos values cos_list percent percent_of_qsize	Applies multiple CoS values to a tail-drop threshold and configures the threshold percentage.
queue-limit dscp values dscp_list percent percent_of_qsize	Applies multiple DSCP values to a tail-drop threshold and configures the threshold percentage.
queue-limit precedence values precedence_list percent percent_of_qsize	Applies multiple precedence values to a tail-drop threshold and configures the threshold percentage.
random-detect cos-based [aggregate]	Enables application of CoS values to a WRED-drop threshold. The aggregate keyword enables use of the values keyword.
random-detect dscp-based [aggregate]	Enables application of DSCP values to a WRED-drop threshold. The aggregate keyword enables use of the values keyword.
random-detect precedence-based [aggregate]	Enables application of precedence values to a WRED-drop threshold. The aggregate keyword enables use of the values keyword.
random-detect multiple-type-based [aggregate]	Enables application of CoS, precedence, and DSCP values to a WRED-drop threshold. The aggregate keyword enables use of the values keyword.
random-detect cos cos_value percent min_percent max_percent	Applies one CoS value to a WRED-drop threshold and configures the threshold percentages.
random-detect dscp dscp_value percent min_percent max_percent	Applies one DSCP value to a WRED-drop threshold and configures the threshold percentages.
random-detect precedence precedence_value percent min_percent max_percent	Applies one DSCP value to a WRED-drop threshold and configures the threshold percentages.
random-detect cos values cos_list percent min_percent max_percent	Applies multiple CoS values to a WRED-drop threshold and configures the threshold percentages; requires the aggregate keyword.
random-detect dscp values dscp_list percent min_percent max_percent	Applies multiple DSCP values to a WRED-drop threshold and configures the threshold percentages; requires the aggregate keyword.
random-detect precedence values precedence_list percent min_percent max_percent	Applies multiple precedence values to a WRED-drop threshold and configures the threshold percentages.

How to Configure Policy-Based Queueing

Note See the “Configuration Examples for Policy-Based Queueing” section for detailed information about which queueing commands are supported by each queue type.

Configuring a Queueing Policy Class Map

To configure a queueing policy class map, perform this task:

	Command	Purpose
Step 1	Router(config)# class-map type lan-queuing match-any class_name	Creates a class map. Create a class map for the thresholds on each type of queue that you are configuring. Give the class map a name that allows you to easily associate it with the queue type and threshold for which you configure it.
Step 2	Router (config-cmap)# match cos cos_value1 [ cos_value2... [ cos_valueN ]]	(Optional) Configures the queueing policy class map to filter based on CoS values. You can enter multiple commands.
Step 3	Router (config-cmap)# match dscp dscp_value1 [ dscp_value2... [ dscp_valueN ]]	(Optional) Configures the queueing policy class map to filter based on DSCP values and enables DSCP-based queueing on the port in the direction that the queueing policy is attached. You can enter multiple commands.
Step 4	Router (config-cmap)# match precedence precedence_value1 [ precedence_value2... [ precedence_valueN ]]	(Optional) Configures the queueing policy class map to filter based on precedence values and enables DSCP-based queueing on the port in the direction that the queueing policy is attached. You can enter multiple commands.
Step 5	Router (config-cmap)# end	Exits configuration mode.

This example shows how to create a class map named cos5 and how to configure filtering to match traffic with CoS 5:

Router# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)# class-map cos5

Router(config-cmap)# match cos 5

Router(config-cmap)# end

Verifying a Queueing Policy Class Map

To verify the queueing policy class map, perform this task:

Command	Purpose
Router# show class-map class_name	Verifies the configuration.

Configuring Queueing Policy Maps

Note ● You can attach one input queueing policy map and one output queueing policy map to an interface.

Queueing policy maps contain one policy-map class for each queue.
Each policy-map class configures a queue.

Creating a Queueing Policy

To create a queueing policy, perform this task:

	Command	Purpose
Step 1	Router(config)# policy-map type lan-queuing policy_name	Creates a policy map.
Step 2	Router(config-pmap)# end	(Optional) Exits policy map class configuration mode.

Configuring a Priority Queue

1p1q4t,1p1q8t,1p7q2t,1p3q8t, 1p7q8t, and 1p7q4t ports have priority queues. To configure the priority queue, perform this task:

	Command	Purpose
Step 1	Router(config-pmap)# class class_map_name	Creates a policy map class.
Step 2	Router(config-pmap-c)# priority	Applies the class map to the priority queue. Note The priority queue is not supported if SRR is enabled.
Step 3	Router(config-pmap-c)# queue-buffers ratio weight	(Optional) Sets queue buffer size.
Step 4	Router(config-pmap-c)# end	(Optional) Exits policy map class configuration mode.

Configuring Nonpriority Queues

The first class class_map_name command that you enter that is not followed by the priority keyword configures the highest numbered nonpriority queue. Subsequent class class_map_name commands configure the remaining nonpriority queues in reverse numerical order (highest-numbered to queue #2). The class class-default command configures queue #1. To configure a nonpriority queue, perform this task:

	Command	Purpose
Step 1	Router(config-pmap)# class { class_map_name \| class-default }	Creates a policy map class. Note Enter a class map name to configure nonpriority queues numbered greater than one. Enter the class-default keyword to configure queue #1.
Step 2	Router(config-pmap-c)# bandwidth [ remaining ] percent percentage	Allocates WRR or DWRR bandwidth. Note Not required on ports that have one queue. The remaining keyword is required on ports that have a priority queue.
Step 3	Router(config-pmap-c)# shape average percent percentage	(Egress queues only) Enables SRR, which allocates limited bandwidth between nonpriority egress queues. See “SRR” in the “Module to Queue Type Mappings” section). Configuring SRR disables the priority queue.
Step 4	Router(config-pmap-c)# queue-limit percent percentage	(Optional) Sets queue buffer size. Note Not required on ports that have one queue.
Step 5	Router(config-pmap-c)# end	(Optional) Exits policy map class configuration mode.

Configuring Thresholds

Threshold Configuration Guidelines and Restrictions

To configure tail drop thresholds, enter queue-limit commands.
For ports that support configuration as either tail-drop or WRED drop:

– Enter queue-limit commands to configure a threshold as tail drop.

– Enter random-detect commands to configure a threshold as WRED drop.

The first queue-limit cos, queue-limit dscp, random-detect cos, or random-detect dscp command that you enter configures threshold #1.
Subsequent commands with different threshold percentage values configure the remaining thresholds in numerical order (from threshold #2 to the highest-numbered threshold).
Subsequent commands with an already configured threshold percentage value apply addition QoS values to the threshold indicated by the percentage value.
Ports configured for DSCP-based queueing use CoS-based queueing for non-IP traffic, IP multicast traffic, and IP unknown unicast flood traffic. In queueing policies that configure DSCP-based queueing, configure CoS-based queueing to provide specific QoS for non-IP traffic, IP multicast traffic, and IP unknown unicast flood traffic.

Configuring a Threshold as Tail-Drop with CoS-Based Queueing

To configure a threshold as tail-drop with CoS-based queueing, perform this task:

	Command	Purpose
Step 1	Router(config-pmap-c)# queue-limit cos { one_value \| values value_list} percent percentage	Applies CoS to a tail-drop threshold and configures the threshold percentage.
Step 2	Router(config-pmap-c)# end	(Optional) Exits policy map class configuration mode.

Configuring a Threshold as WRED-Drop with CoS-Based Queueing

To configure a threshold as WRED-drop with CoS-based queueing, perform this task:

	Command	Purpose
Step 1	Router(config-pmap-c)# random-detect cos-based [ aggregate ]	Enables application of CoS values to a WRED-drop threshold. Enter the aggregate keyword to configure multiple CoS values on the threshold with the values keyword.
Step 2	Router(config-pmap-c)# random-detect cos { one_value \| values value_list} percent min_% max_%	Applies CoS to a WRED-drop threshold and configures the threshold percentage.
Step 3	Router(config-pmap-c)# end	(Optional) Exits policy map class configuration mode.

Configuring a Threshold as Tail-Drop with DSCP-Based Queueing

To configure a threshold as tail-drop with DSCP-based queueing, perform this task:

	Command	Purpose
Step 1	Router(config-pmap-c)# queue-limit multiple-type-based	(Optional) Enables application of CoS, DSCP, or precedence values to a tail-drop threshold.
Step 2	Router(config-pmap-c)# queue-limit { cos \| dscp \| precedence } { one_value \| values value_list} percent percentage	Applies QoS values to a tail-drop threshold and configures the threshold percentage.
Step 3	Router(config-pmap-c)# end	(Optional) Exits policy map class configuration mode.

Configuring a Threshold as WRED-Drop with DSCP-Based Queueing

To configure a threshold as WRED-drop with DSCP-based queueing, perform this task:

	Command	Purpose
Step 1	Router(config-pmap-c)# random-detect { dscp-based \| precedence-based \| multiple-type-based } [ aggregate ]	Enables application of QoS values to a WRED-drop threshold. Note Enter the dscp-based keyword to enable application of DSCP values to a WRED-drop threshold. Enter the precedence-based keyword to enable application of precedence values to a WRED-drop threshold. Enter the multiple-type-based keyword to enable application of both CoS, DSCP, or precedence values to a WRED-drop threshold. Enter the aggregate keyword to configure multiple QoS values on the threshold with the values keyword.
Step 2	Router(config-pmap-c)# random-detect { cos \| dscp \| precedence } { one_value \| values value_list} percent min_% max_%	Applies QoS values to a WRED-drop threshold and configures the threshold percentage.
Step 3	Router(config-pmap-c)# end	(Optional) Exits policy map class configuration mode.

Command

Purpose

Step 1

Router(config-pmap-c)# random-detect { dscp-based | precedence-based | multiple-type-based } [ aggregate ]

Enables application of QoS values to a WRED-drop threshold.

Note

Enter the dscp-based keyword to enable application of DSCP values to a WRED-drop threshold.
Enter the precedence-based keyword to enable application of precedence values to a WRED-drop threshold.
Enter the multiple-type-based keyword to enable application of both CoS, DSCP, or precedence values to a WRED-drop threshold.
Enter the aggregate keyword to configure multiple QoS values on the threshold with the values keyword.

Step 2

Router(config-pmap-c)# random-detect { cos | dscp | precedence } { one_value | values value_list} percent min_% max_%

Applies QoS values to a WRED-drop threshold and configures the threshold percentage.

Step 3

Router(config-pmap-c)# end

(Optional) Exits policy map class configuration mode.

Verifying a Queueing Policy Map

Use the show policy-map policy_name to verify the configuration.

Attaching a Queueing Policy Map to an Interface

To attach a queueing policy to an interface, perform this task:

	Command	Purpose
Step 1	Router(config)# interface type slot/port	Selects the interface to configure.
Step 2	Router(config-if)# service-policy type lan-queuing [ input \| output ] policy_map_name	Attaches a queueing policy to the interface.
Step 3	Router(config-if)# end	Exits configuration mode.

Use the show policy-map interface command to verify the configuration.

Configuration Examples for Policy-Based Queueing

Queueing Policy Sample Configuration

Without comments:

policy-map type lan-queuing p1

class cos5

priority

class cos123

bandwidth remaining percent 25

queue-limit cos 2 percent 20

queue-limit cos 3 percent 30

class class-default

queue-limit cos 6 percent 60

With comments:

policy-map type lan-queuing p1 ! For 1p3q8t

class cos5 ! Configured to filter CoS 5

!The filtering configured in the class map selects the values that go to the queue

priority ! Applies the class map to the priority queue (#4)

!First non-priority class applies to highest-numbered non-priority queue (#3)

class cos123 ! Configured to filter CoS 1, 2, and 3

!The filtering configured in the class map selects the values that go to the queue

!'remaining' keyword required on ports that have a priority queue

bandwidth remaining percent 25

!First queue-limit command assigns CoS 2 to threshold #1 and configures it at 20%

queue-limit cos 2 percent 20

!Any other queue-limit command with the same percentage

!applies additional configuration to this threshold

!Next queue-limit command with different percentage value configures the next threshold

!Assigns CoS 3 to threshold #2 and configures it at 30%

queue-limit cos 3 percent 30

!Any other queue-limit command with the same percentage

!applies additional configuration to this threshold

!Thresholds 3-8 are unconfigured

!All unconfigured thresholds are at 100%

!No explicit configuration provided for CoS 1: defaults to last threshold

!End of queue 3 configuration

!Queue 2 is unconfigured

class class-default ! applies to queue #1

!'class-default' gets all remaining CoS values:

!0, 4, 6, and 7

!Threshold 1 is explicitly configured:

queue-limit cos 6 percent 50

!Remaining thresholds (2-8) are not configured by the queueing policy

!and cannot be configured by anything else

!No explicit configuration provided for CoS 0, 4, and 7:

!CoS values not explicitly configured default to the last threshold

Queueing Policy Commands Supported by Each Queue Type

1q2t, 1q8t Ingress Queue Supported Commands

Note ● Supports CoS-based queueing with tail-drop thresholds.

Unsupported commands are included in this section as comments.

policy-map type lan-queuing policy_map_name ! For 1q2t, 1q8t

Nonpriority queue 1 policy commands:

class class-default ! Receives all CoS values.

! bandwidth percent percentage ! WRR or DWRR bandwidth allocation.

! queue-limit percent percentage ! Queue buffer size.

Nonpriority queue threshold configuration (repeat to configure sequential thresholds):

! queue-limit multiple-type-based

! Enables application of CoS, precedence, and DSCP values

! to a tail-drop threshold.

queue-limit cos {one_value | values value_list} percent percentage

! queue-limit dscp {one_value | values value_list} percent percentage

! Applies one DSCP value to a tail-drop threshold

! and configures the threshold percentage

! random-detect cos-based [aggregate]

! Enables application of CoS values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect dscp-based [aggregate]

! Enables application of DSCP values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect precedence-based [aggregate]

! Enables application of precedence values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect multiple-type-based [aggregate]

! Enables application of CoS, precedence, and DSCP values

! to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect cos {one_value | values value_list} percent min_% max_%

! Applies CoS to a WRED-drop threshold and configures the threshold percentages.

! random-detect dscp {one_value | values value_list} percent min_% max_%

! Applies DSCP to a WRED-drop threshold and configures the threshold percentages.

! random-detect {precedence one_value | values precedence value_list} percent min_% max_%

! Applies DSCP to a WRED-drop threshold and configures the threshold percentages.

2q8t Ingress Queue Supported Commands

Note ● Supports CoS-based queueing with tail-drop thresholds.

Unsupported commands are included in this section as comments.

policy-map type lan-queuing policy_map_name ! For 2q8t, 8q8t

Class commands for nonpriority queues numbered higher than 1—Configures queues in reverse numerical order; repeat to configure the next queue:

class class_map_name ! Receives CoS values filtered by class_map_name.

Class command for queue #1:

class class-default ! Receives all remaining CoS values.

Nonpriority queue configuration commands:

bandwidth percent percentage ! WRR or DWRR bandwidth allocation.

queue-limit percent percentage ! Queue buffer size.

Nonpriority queue threshold configuration—Repeat to configure sequential thresholds in each queue:

! queue-limit multiple-type-based

! Enables application of CoS, precedence, and DSCP values to a tail-drop threshold.

queue-limit cos {one_value | values value_list} percent percentage

! Applies CoS to a tail-drop threshold and configures the threshold percentage

! queue-limit dscp {one_value | values value_list} percent percentage

! Applies one DSCP value to a tail-drop threshold

! and configures the threshold percentage

! random-detect cos-based [aggregate]

! Enables application of CoS values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect dscp-based [aggregate]

! Enables application of DSCP values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect precedence-based [aggregate]

! Enables application of precedence values to a WRED-drop threshold.

! random-detect multiple-type-based [aggregate]

! Enables application of CoS, precedence, and DSCP values

! to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect cos {one_value | values value_list} percent min_% max_%

! Applies CoS to a WRED-drop threshold and configures the threshold percentages.

! random-detect dscp {one_value | values value_list} percent min_% max_%

! Applies DSCP to a WRED-drop threshold and configures the threshold percentages.

! random-detect {precedence one_value | values precedence value_list} percent min_% max_%

! Applies DSCP to a WRED-drop threshold and configures the threshold percentages.

8q4t Ingress Queue Supported Commands

Note ● Supports CoS-based, DSCP-based, and precedence-based queueing with tail-drop and WRED-drop thresholds.

Unsupported commands are included in this section as comments.
In releases where CSCts82932 is not resolved, do not use the default DSCP-based queue mapping for 8q4t ingress queues unless you configure supporting bandwidth and queue limits.

policy-map type lan-queuing policy_map_name ! For 8q4t

Class commands for nonpriority queues numbered higher than 1—Configures queues in reverse numerical order; repeat to configure the next queue:

class class_map_name

! Receives QoS values (CoS, DSCP, precedence) values filtered by class_map_name.

Class command for queue #1:

class class-default ! Receives all remaining QoS values (CoS, DSCP, precedence).

Nonpriority queue configuration commands:

bandwidth percent percentage ! WRR or DWRR bandwidth allocation.

queue-limit percent percentage ! Queue buffer size.

Nonpriority queue threshold configuration—Repeat to configure sequential thresholds in each queue:

queue-limit multiple-type-based

! Enables application of CoS, precedence, and DSCP values to a tail-drop threshold.

queue-limit cos {one_value | values value_list} percent percentage

! Applies CoS to a tail-drop threshold and configures the threshold percentage

queue-limit dscp {one_value | values value_list} percent percentage

! Applies one DSCP value to a tail-drop threshold

! and configures the threshold percentage

random-detect cos-based [aggregate]

! Enables application of CoS values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

random-detect dscp-based [aggregate]

! Enables application of DSCP values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

random-detect precedence-based [aggregate]

! Enables application of precedence values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

random-detect multiple-type-based [aggregate]

! Enables application of CoS, precedence, and DSCP values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

random-detect cos {one_value | values value_list} percent min_% max_%

! Applies CoS to a WRED-drop threshold and configures the threshold percentages.

random-detect dscp {one_value | values value_list} percent min_% max_%

! Applies DSCP to a WRED-drop threshold and configures the threshold percentages.

random-detect {precedence one_value | values precedence value_list} percent min_% max_%

! Applies DSCP to a WRED-drop threshold and configures the threshold percentages.

8q8t Ingress Queue Supported Commands

Note ● Supports CoS-based queueing with tail-drop or WRED-drop thresholds.

Unsupported commands are included in this section as comments.

policy-map type lan-queuing policy_map_name ! For 1p1q8t

Priority queue:

class class_map_name ! Receives CoS values filtered by class_map_name.

priority ! Applies the class map to the priority queue

Nonpriority queue policy commands:

class class-default ! Receives all remaining CoS values.

! bandwidth remaining percent percentage ! WRR or DWRR bandwidth allocation.

! queue-limit percent percentage ! Queue buffer size.

Nonpriority queue threshold configuration—Repeat to configure sequential thresholds:

! queue-limit multiple-type-based

! Enables application of CoS, precedence, and DSCP values to a tail-drop threshold.

queue-limit cos {one_value | values value_list} percent percentage

! Applies CoS to a tail-drop threshold and configures the threshold percentage

! queue-limit dscp {one_value | values value_list} percent percentage

! Applies one DSCP value to a tail-drop threshold

! and configures the threshold percentage

random-detect cos-based [aggregate]

! Enables application of CoS values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect dscp-based [aggregate]

! Enables application of DSCP values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect precedence-based [aggregate]

! Enables application of precedence values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect multiple-type-based [aggregate]

! Enables application of CoS, precedence, and DSCP values

! to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

random-detect cos {one_value | values value_list} percent min_% max_%

! Applies CoS to a WRED-drop threshold and configures the threshold percentages.

! random-detect dscp {one_value | values value_list} percent min_% max_%

! Applies DSCP to a WRED-drop threshold and configures the threshold percentages.

! random-detect {precedence one_value | values precedence value_list} percent min_% max_%

! Applies DSCP to a WRED-drop threshold and configures the threshold percentages.

1p1q4t Ingress Queue Supported Commands

Note ● Supports CoS-based queueing with tail-drop thresholds.

Unsupported commands are included in this section as comments.

policy-map type lan-queuing policy_map_name ! For 1p1q4t

Priority queue:

class class_map_name ! Receives CoS values filtered by class_map_name.

priority ! Applies the class map to the priority queue

Nonpriority queue policy commands:

class class-default ! Receives all remaining CoS values.

! bandwidth remaining percent percentage ! WRR or DWRR bandwidth allocation.

! queue-limit percent percentage ! Queue buffer size.

Nonpriority queue threshold configuration—Repeat to configure sequential thresholds:

! queue-limit multiple-type-based

! Enables application of CoS, precedence, and DSCP values

! to a tail-drop threshold.

queue-limit cos {one_value | values value_list} percent percentage

! Applies CoS to a tail-drop threshold and configures the threshold percentage

! queue-limit dscp {one_value | values value_list} percent percentage

! Applies one DSCP value to a tail-drop threshold

! and configures the threshold percentage

! random-detect cos-based [aggregate]

! Enables application of CoS values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect dscp-based [aggregate]

! Enables application of DSCP values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect precedence-based [aggregate]

! Enables application of precedence values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect multiple-type-based [aggregate]

! Enables application of CoS, precedence, and DSCP values

! to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect cos {one_value | values value_list} percent min_% max_%

! Applies CoS to a WRED-drop threshold and configures the threshold percentages.

! random-detect dscp {one_value | values value_list} percent min_% max_%

! Applies DSCP to a WRED-drop threshold and configures the threshold percentages.

! random-detect {precedence one_value | values precedence value_list} percent min_% max_%

! Applies DSCP to a WRED-drop threshold and configures the threshold percentages.

1p1q8t Ingress Queue Supported Commands

Note ● Supports CoS-based queueing with tail-drop or WRED-drop thresholds.

Unsupported commands are included in this section as comments.

policy-map type lan-queuing policy_map_name ! For 1p1q8t

Priority queue:

class class_map_name ! Receives CoS values filtered by class_map_name.

priority ! Applies the class map to the priority queue

Nonpriority queue policy commands:

class class-default ! Receives all remaining CoS values.

! bandwidth remaining percent percentage ! WRR or DWRR bandwidth allocation.

! queue-limit percent percentage ! Queue buffer size.

Nonpriority queue threshold configuration—Repeat to configure sequential thresholds:

! queue-limit multiple-type-based

! Enables application of CoS, precedence, and DSCP values to a tail-drop threshold.

queue-limit cos {one_value | values value_list} percent percentage

! Applies CoS to a tail-drop threshold and configures the threshold percentage

! queue-limit dscp {one_value | values value_list} percent percentage

! Applies one DSCP value to a tail-drop threshold

! and configures the threshold percentage

random-detect cos-based [aggregate]

! Enables application of CoS values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect dscp-based [aggregate]

! Enables application of DSCP values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect precedence-based [aggregate]

! Enables application of precedence values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect multiple-type-based [aggregate]

! Enables application of CoS, precedence, and DSCP values

! to a WRED-drop threshold.

random-detect cos {one_value | values value_list} percent min_% max_%

! Applies CoS to a WRED-drop threshold and configures the threshold percentages.

! random-detect dscp {one_value | values value_list} percent min_% max_%

! Applies DSCP to a WRED-drop threshold and configures the threshold percentages.

! random-detect {precedence one_value | values precedence value_list} percent min_% max_%

! Applies DSCP to a WRED-drop threshold and configures the threshold percentages.

1p7q2t Ingress Queue Supported Commands

Note ● Supports CoS-based, DSCP-based, and precedence-based queueing with tail-drop and WRED-drop thresholds.

Unsupported commands are included in this section as comments.

policy-map type lan-queuing policy_map_name ! For 1p7q2t

Priority queue:

class class_map_name

! Receives QoS values (CoS, DSCP, precedence) values filtered by class_map_name.

priority ! Applies the class map to the priority queue

Class commands for nonpriority queues numbered higher than 1—Configures queues in reverse numerical order; repeat to configure the next queue:

class class_map_name

! Receives QoS values (CoS, DSCP, precedence) values filtered by class_map_name.

Class command for queue #1:

class class-default ! Receives all remaining QoS values (CoS, DSCP, precedence).

Nonpriority queue configuration commands:

bandwidth percent percentage ! WRR or DWRR bandwidth allocation.

queue-limit percent percentage ! Queue buffer size.

Nonpriority queue threshold configuration—Repeat to configure sequential thresholds in each queue:

queue-limit multiple-type-based

! Enables application of CoS, precedence, and DSCP values to a tail-drop threshold.

queue-limit cos {one_value | values value_list} percent percentage

! Applies CoS to a tail-drop threshold and configures the threshold percentage

queue-limit dscp {one_value | values value_list} percent percentage

! Applies one DSCP value to a tail-drop threshold

! and configures the threshold percentage

1p3q8t Egress Queue Supported Commands

Note ● Supports CoS-based queueing with tail-drop and WRED-drop thresholds.

Unsupported commands are included in this section as comments.

policy-map type lan-queuing policy_map_name ! For 1p3q8t

Priority queue:

class class_map_name ! Receives CoS values filtered by class_map_name.

priority ! Applies the class map to the priority queue

Class commands for nonpriority queues numbered higher than 1—Configures queues in reverse numerical order; repeat to configure the next queue:

class class_map_name ! Receives CoS values filtered by class_map_name.

Class command for queue #1:

class class-default ! Receives all remaining CoS values.

Nonpriority queue configuration commands:

bandwidth percent percentage ! WRR or DWRR bandwidth allocation.

! shape average percent percentage ! SRR bandwidth allocation.

queue-limit percent percentage ! Queue buffer size.

Nonpriority queue threshold configuration—Repeat to configure sequential thresholds:

! queue-limit multiple-type-based

! Enables application of CoS, precedence, and DSCP values to a tail-drop threshold.

queue-limit cos {one_value | values value_list} percent percentage

! Applies CoS to a tail-drop threshold and configures the threshold percentage

! queue-limit dscp {one_value | values value_list} percent percentage

! Applies one DSCP value to a tail-drop threshold

! and configures the threshold percentage

random-detect cos-based [aggregate]

! Enables application of CoS values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect dscp-based [aggregate]

! Enables application of DSCP values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect precedence-based [aggregate]

! Enables application of precedence values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect multiple-type-based [aggregate]

! Enables application of CoS, precedence, and DSCP values

! to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

random-detect cos {one_value | values value_list} percent min_% max_%

! Applies CoS to a WRED-drop threshold and configures the threshold percentages.

! random-detect dscp {one_value | values value_list} percent min_% max_%

! Applies DSCP to a WRED-drop threshold and configures the threshold percentages.

! random-detect {precedence one_value | values precedence value_list} percent min_% max_%

! Applies DSCP to a WRED-drop threshold and configures the threshold percentages.

1p7q8t Egress Queue Supported Commands

Note ● Supports CoS-based queueing with tail-drop and WRED-drop thresholds.

Unsupported commands are included in this section as comments.

policy-map type lan-queuing policy_map_name ! For 1p7q8t

Priority queue:

class class_map_name ! Receives CoS values filtered by class_map_name.

priority ! Applies the class map to the priority queue

Class commands for nonpriority queues numbered higher than 1—Configures queues in reverse numerical order; repeat to configure the next queue:

class class_map_name ! Receives CoS values filtered by class_map_name.

Class command for queue #1:

class class-default ! Receives all remaining CoS values.

Nonpriority queue configuration commands:

bandwidth percent percentage ! WRR or DWRR bandwidth allocation.

! shape average percent percentage ! SRR bandwidth allocation.

queue-limit percent percentage ! Queue buffer size.

Nonpriority queue threshold configuration—Repeat to configure sequential thresholds:

! queue-limit multiple-type-based

! Enables application of CoS, precedence, and DSCP values to a tail-drop threshold.

queue-limit cos {one_value | values value_list} percent percentage

! Applies CoS to a tail-drop threshold and configures the threshold percentage

! queue-limit dscp {one_value | values value_list} percent percentage

! Applies one DSCP value to a tail-drop threshold

! and configures the threshold percentage

random-detect cos-based [aggregate]

! Enables application of CoS values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect dscp-based [aggregate]

! Enables application of DSCP values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect precedence-based [aggregate]

! Enables application of precedence values to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

! random-detect multiple-type-based [aggregate]

! Enables application of CoS, precedence, and DSCP values

! to a WRED-drop threshold.

! The 'aggregate' keyword allows use of the 'values' keyword

random-detect cos {one_value | values value_list} percent min_% max_%

! Applies CoS to a WRED-drop threshold and configures the threshold percentages.

! random-detect dscp {one_value | values value_list} percent min_% max_%

! Applies DSCP to a WRED-drop threshold and configures the threshold percentages.

! random-detect {precedence one_value | values precedence value_list} percent min_% max_%

! Applies DSCP to a WRED-drop threshold and configures the threshold percentages.

1p7q4t Ingress or Egress Queue Supported Commands

Note ● Supports CoS-based, DSCP-based, and precedence-based queueing with tail-drop and WRED-drop thresholds. Supports SRR or DWRR dequeueing.

Unsupported commands are included in this section as comments.

Priority queue:

class class_map_name

! Receives QoS values (CoS, DSCP, precedence) values filtered by class_map_name.

priority ! Applies the class map to the priority queue

! Not supported if SRR mode is enabled.

queue-limit percent percentage ! Queue buffer size.

Class commands for nonpriority queues numbered higher than 1—Configures queues in reverse numerical order; repeat to configure the next queue:

class class_map_name

! Receives QoS values (CoS, DSCP, precedence) values filtered by class_map_name.

Class command for queue #1:

class class-default ! Receives all remaining QoS values (CoS, DSCP, precedence).

Nonpriority queue configuration commands:

shape average percent percentage

! Enables SRR on nonpriority egress queues.

bandwidth remaining percent percentage

! DWRR bandwidth allocation.

queue-limit percent percentage ! Queue buffer size.

Nonpriority queue threshold configuration—Repeat to configure sequential thresholds in each queue: