Users Guide

pfc no-drop queuesqueue-range

The maximum number of lossless queues globally supported on a port is 2.

You cannot congure PFC no-drop queues on an interface on which a DCB map with PFC enabled has been applied, or which is

already congured for PFC using the pfc priority command.

Data Center Bridging: Default Conguration

Before you congure PFC and ETS on a switch see the priority group setting taken into account the following default settings:

DCB is enabled.

PFC and ETS are globally enabled by default.

The default dot1p priority-queue assignments are applied as follows:

Dell(conf)#do show qos dot1p-queue-mapping

Dot1p Priority : 0 1 2 3 4 5 6 7

Queue : 0 0 0 1 2 3 3 3

Dell(conf)#

NOTE: In Dell Networking OS we support 4 data queues.

PFC is not applied on specic dot1p priorities.

ETS: Equal bandwidth is assigned to each port queue and each dot1p priority in a priority group.

Data Center Bridging: Auto-DCB-Enable Mode

On an Aggregator in standalone or VLT modes, the default mode of operation for data center bridging on Ethernet ports is auto-DCB-

enable mode. In this mode, Aggregator ports detect whether peer devices support CEE or not, and enable ETS and PFC or link-level ow

control accordingly:

• Interfaces come up with DCB disabled and link-level ow control enabled to control data transmission between the Aggregator and

other network devices (see Flow Control Using Ethernet Pause Frames). When DCB is disabled on an interface, PFC, and ETS are also

disabled.

• When DCBx protocol packets are received, interfaces automatically enable DCB and disable link-level ow control.

DCB is required for PFC, ETS, DCBx, and FCoE initialization protocol (FIP) snooping to operate.

NOTE

: Normally, interfaces do not ap when DCB is automatically

enabled.

DCB processes VLAN-tagged packets and dot1p priority values. Untagged packets are treated with a dot1p priority of 0.

For DCB to operate eectively, ingress trac is classied according to its dot1p priority so that it maps to dierent data queues. The dot1p-

queue assignments used on an Aggregator are shown in Table 6-1 in dcb enable auto-detect on-next-reload Command Example QoS dot1p

Trac Classication and Queue Assignment.

When DCB is Disabled (Default) By default, Aggregator interfaces operate with DCB disabled and link-level ow control enabled. When an

interface comes up, it is automatically congured with:

• Flow control enabled on input interfaces.

• A DCB-MAP policy is applied with PFC disabled.

The following example shows a default interface conguration with DCB disabled and link-level ow control enabled.

show interfaces Command Example: DCB disabled and Flow Control enabled

Dell#show running-config interface te 0/4

Data Center Bridging (DCB)