Configuration manual

You can enable any number of 802.1p priorities for PFC. Queues to which PFC priority traffic is mapped
are lossless by default. Traffic may be interrupted due to an interface flap (going down and coming up)
when you reconfigure the lossless queues for no-drop priorities in a PFC input policy and reapply the
policy to an interface.
To apply PFC, a PFC peer must support the configured priority traffic (as detected by DCBx).
To honor a PFC pause frame multiplied by the number of PFC-enabled ingress ports, the minimum link
delay must be greater than the round-trip transmission time the peer requres.
If you apply an input policy with PFC disabled (no pfc mode on):
• You can enable link-level flow control on the interface (refer to Enabling Pause Frames). To delete the
input policy, first disable link-level flow control. PFC is then automatically enabled on the interface
because an interface is by default PFC-enabled.
• PFC still allows you to configure lossless queues on a port to ensure no-drop handling of lossless
traffic (refer to Configuring Lossless Queues).
NOTE: You cannot enable PFC and link-level flow control at the same time on an interface.
When you apply an input policy to an interface, an error message displays if:
• The PFC dot1p priorities result in more than two lossless port queues globally on the switch.
• Link-level flow control is already enabled. You cannot be 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.
A DCB input policy for PFC applied to an interface may become invalid if you reconfigure dot1p-queue
mapping (refer to the Create Input Policy Maps section in the Quality of Service (QoS) chapter). This
situation occurs when the new dot1p-queue assignment exceeds the maximum number (2) of lossless
queues supported globally on the switch. In this case, all PFC configurations received from PFC-enabled
peers are removed and resynchronized with the peer devices.
Traffic may be interrupted when you reconfigure PFC no-drop priorities in an input policy or reapply the
policy to an interface.
The Dell Networking OS does not support MACsec Bypass Capability (MBC).
Configuring Lossless Queues
DCB also supports the manual configuration of lossless queues on an interface when PFC mode is turned
off and priority classes are disabled in a DCB input policy applied to the interface.
Prerequisite: A DCB input policy with PFC configuration is applied to the interface with the following
conditions:
• PFC mode is off (no pfc mode on).
• No PFC priority classes are configured (no pfc priority priority-range).
The configuration of no-drop queues provides flexibility for ports on which PFC is not needed but
lossless traffic should egress from the interface.
Lossless traffic egresses out the no-drop queues. Ingress dot1p traffic from PFC-enabled interfaces is
automatically mapped to the no-drop egress queues.
1. Enter INTERFACE Configuration mode.
CONFIGURATION mode
Data Center Bridging (DCB)
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