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Priority Commands:
Dell™ PowerEdge™ 1655MC Integrated Switch User's Guide

The commands described in this section allow you to specify which data packets have greater precedence when traffic is buffered in the switch due to congestion. This switch supports Class of Service (CoS) with four priority queues for each port. Data packets in a port’s high-priority queue will be transmitted before those in the lower-priority queues. You can set the default priority for each interface.

switchport priority default

Use this command to set a priority for incoming untagged frames, or the priority of frames received by the device connected to the specified interface. Use the no form to restore the default value.

Syntax

switchport priority default default-priority-id
no switchport priority default

default-priority-id - The priority number for untagged ingress traffic.
The priority is a number from 0 to 7. Seven is the highest priority.

Default Setting

The priority is not set, and the default value for untagged frames received on the interface is zero. The switch is not instructed what to do with the priority.

Command Mode

Interface Configuration (Ethernet, Port Channel)

Command Usage

• The precedence for priority mapping is IP Port, IP Precedence or IP Differentiated Services Code Point (DSCP), and default switchport priority.
• The default port priority applies if the incoming frame is an untagged frame received from a VLAN trunk or a static-access port. This priority does not apply to IEEE 802.1Q VLAN tagged frames. If the incoming frame is an IEEE 802.1Q VLAN tagged frame, the IEEE 802.1p User Priority bits will be used.
• This switch provides four priority queues for each port. It is configured to use Weighted Round Robin, which can viewed with the queue bandwidth command. Inbound frames that do not have VLAN tags are tagged with the input port’s default ingress user priority, and then placed in the appropriate priority queue at the output port. The default priority for all ingress ports is zero. Therefore, any inbound frames that do not have priority tags will be placed in queue 0 of the output port. (Note that if the output port is an untagged member of the associated VLAN, these frames are stripped of all VLAN tags prior to transmission.)

Example

The following example shows how to set the default priority on port 3 to 5:

(config)#interface ethernet 1/3 (config-if)#switchport priority default 5

queue cos-map

Use this command to assign Class of Service (CoS) values to the CoS priority queues. Use the no form set the CoS map to the default values.

Syntax

queue cos-map queue_id [cos1 ... cosn]
no queue cos-map

• queue_id - The queue id of the CoS priority queue.
  Ranges are 0 to 3, where 3 is the highest CoS priority queue.
• cos1 .. cosn - The CoS values that are mapped to the queue id. It is a space-separated list of numbers. The CoS value is a number from 0 to 7, where 7 is the highest priority.

Default Setting

This switch supports Class of Service by using four priority queues, with Weighted Fair Queuing for each port. Up to 8 separate traffic classes are defined in IEEE 802.1p. The default priority levels are assigned according to recommendations in the IEEE 802.1p standard as shown in the following table.

Table 1. Priority to Queue Mapping

	Queue
	1	2	3	4
Priority		0
	1
	2
		3
			4
			5
				6
				7

Command Mode

Interface Configuration (Ethernet, Port Channel)

Command Usage

CoS assigned at the ingress port is used to select a CoS priority at the egress port.

NOTE: The queue cos-map command sets the CoS values for the entire switch. However, you must first enter Interface Configuration mode for any interface to use this command.

Example

The following example shows how to map CoS values 0, 1 and 2 to CoS priority queue 0, value 3 to CoS priority queue 1, values 4 and 5 to CoS priority queue 2, and values 6 and 7 to CoS priority queue 3:

(config)#interface ethernet 1/7 (config-if)#queue cos-map 0 0 1 2 (config-if)#queue cos-map 1 3 (config-if)#queue cos-map 2 4 5 (config-if)#queue cos-map 3 6 7 (config-if)#

Related Commands

show queue cos-map

show queue cos-map

Use this command to show the class of service priority map.

Syntax

show queue cos-map [interface]

• interface
  • ethernet unit/port
    • unit - This is device 1.
    • port - Port number.
  • port-channel channel-id (Range: 1-6)

Default Setting

None

Command Mode

Privileged Exec

Example

#show queue cos-map ethernet 1/11 Information of Eth 1/11  Queue ID Class of service  -------- ----------------     0     1 2     1     0 3     2     4 5     3     6 7 #

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