Users Guide

Data Center Bridging: Default Configuration

Before you configure 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)#

PFC is not applied on specific dot1p priorities.

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

To configure PFC and ETS parameters on an S6000 interface, you must specify the PFC mode, the ETS

bandwidth allocation for a priority group, and the 802.1p priority-to-priority group mapping in a DCB

map. No default PFC and ETS settings are applied to Ethernet interfaces.

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 flow control accordingly:

• Interfaces come up with DCB disabled and link-level flow 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

flow control.

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

NOTE: Normally, interfaces do not flap 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 effectively, ingress traffic is classified according to its dot1p priority so that it maps to

different 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 Traffic Classification and Queue

Assignment.

When DCB is Disabled (Default) By default, Aggregator interfaces operate with DCB disabled and link-

level flow control enabled. When an interface comes up, it is automatically configured with:

Data Center Bridging (DCB)