Administrator Guide

the CRC and discards counters. (These ingress interfaces receiving pfc-enabled traffic have an egress interface that has a compatible
PFC configuration).
NOTE: DCB maps are supported only on physical Ethernet interfaces.
• To remove a DCB map, including the PFC configuration it contains, use the no dcb map command in Interface configuration mode.
• To disable PFC operation on an interface, use the no pfc mode on command in DCB-Map configuration mode.
• Traffic may be interrupted when you reconfigure PFC no-drop priorities in a DCB map or re-apply the DCB map to an interface.
• For PFC to be applied, the configured priority traffic must be supported by a PFC peer (as detected by DCBx).
• If you apply a DCB map with PFC disabled (pfc off), you can enable link-level flow control on the interface using the
flowcontrol rx on tx on command. To delete the DCB map, first disable link-level flow control. PFC is then automatically
enabled on the interface because an interface is PFC-enabled by default.
• To ensure no-drop handling of lossless traffic, PFC allows you to configure lossless queues on a port (see Configuring Lossless
Queues).
• When you configure a DCB map, an error message is displayed if the PFC dot1p priorities result in more than two lossless queues.
• 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
242 Data Center Bridging (DCB)