Administrator Guide

Data Center Technology Commands 1206
The effective default behavior on an interface enabled for PFC without a no-
drop priority is that no flow control (legacy or PFC) is enabled. If the user
enables PFC but does not create any no-drop priorities, the interface will not
be lossless.
Changing the drop and no-drop capabilities on an interface, either in flow
control or priority flow control, may require that all ports briefly drop link.
The priority to flow control group cannot be changed while traffic is running.
When 802.3 link flow control is enabled, all priorities are mapped to a single
flow control group. When Qbb is enabled, the priorities are each mapped into
their own flow control group, where lossless groups have additional buffer to
handle the round trip delay for flow control. In order to minimize the impact,
the link will only be dropped when changing between 802.3 and Qbb.
Commands in this Section
This section explains the following commands:
priority-flow-control mode
Use the priority-flow-control mode on command in Datacenter-Bridging
Configuration mode to enable Priority-Flow-Control (PFC) on an interface.
To disable Priority-Flow-Control, use the no form of the command.
Syntax
priority-flow-control mode on
priority-flow-control mode off
no priority-flow-control mode
• on—Enable PFC on the interface.
• off—Disable PFC on the interface.
Data Center Bridging Capability Exchange Commands
priority-flow-control priority
clear priority-flow-control statistics
show interfaces priority-flow-control