Deployment Guide

● When you apply a DCB map, an error message is displayed if link-level flow control is already enabled on an interface. You
cannot enable PFC and link-level flow control at the same time on an interface.
● In a switch stack, configure all stacked ports with the same PFC configuration.
● Dell EMC Networking OS allows you to change the default dot1p priority-queue assignments only if the change satisfies the
following requirements in DCB maps already applied to the interfaces:
● All 802.1p priorities mapped to the same queue must be in the same priority group.
● A maximum of two PFC-enabled, lossless queues are supported on an interface.
Otherwise, the reconfiguration of a default dot1p-queue assignment is rejected.
● To ensure complete no-drop service, apply the same PFC parameters on all PFC-enabled peers.
PFC Prerequisites and Restrictions
On a switch, PFC is globally enabled by default, but not applied on specific 802.1p priorities. To enable PFC on 802.1p priorities,
create a DCB map.
The following prerequisites and restrictions apply when you configure PFC in a DCB map:
● You can enable PFC on a maximum of two priority queues on an interface. Enabling PFC for dot1p priorities configures the
corresponding port queue as lossless.
● You cannot enable PFC and link-level flow control at the same time on an interface.
Configuring PFC without a DCB Map
In a network topology that uses the default ETS bandwidth allocation (assigns equal bandwidth to each priority), you can also
enable PFC for specific dot1p-priorities on individual interfaces without using a DCB map. This type of DCB configuration is
useful on interfaces that require PFC for lossless traffic, but do not transmit converged Ethernet traffic.
Table 17. Configuring PFC without a DCB Map
Step Task Command Command Mode
1 Enter interface configuration mode on an Ethernet
port.
interface interface-
type}
CONFIGURATION
2 Enable PFC on specified priorities. Range: 0-7. Default:
None.
Maximum number of lossless queues supported on an
Ethernet port: 2.
Separate priority values with a comma. Specify a
priority range with a dash, for example: pfc priority
3,5-7
1. You cannot configure PFC using the pfc
priority command on an interface on which a
DCB map has been applied or which is already
configured for lossless queues (pfc no-drop
queues command).
pfc priority priority-
range
INTERFACE
Configuring Lossless Queues
DCB also supports the manual configuration of lossless queues on an interface when PFC mode is disabled in a DCB map, apply
the map on the interface. The configuration of no-drop queues provides flexibility for ports on which PFC is not needed, but
lossless traffic should egress from the interface.
Data Center Bridging (DCB)
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