Reference Guide

Traffic may be interrupted due to an interface flap (going down and coming up) when you reconfigure
lossless queues on no-drop priorities in an input policy and re-apply the policy to an interface.
In S6000, any pfc-dot1p priorities configured on a given interface need not be the same across the
system. In other words, lossless queue limit is applicable on a per-port level and not on the global-config
context. For example, one of the Te/Fo interfaces can have pfc-dot1p priorities as 2 and 3. Whereas, the
other Te/Fo interface(s) can have its pfc-dot1p priorities as 4 and 5.
It is the user responsibility to have symmetric PFC configurations on the interfaces involved in a particular
PFC-enabled traffic-flow to obtain lossless behavior
Configuring the PFC Buffer in a Switch Stack
In a switch stack, you must configure all stacked ports with the same PFC configuration. In addition, you
must configure a separate buffer of memory allocated exclusively to a service pool accessed by queues
on which priority-based control flows are mapped.
These PFC-enabled queues ensure the lossless transmission of storage and server traffic. The buffer
required for the PFC service pool is calculated based on the number of ports and port queues used by
PFC traffic.
You can configure the size of the PFC buffer for all switches in a stack or all port pipes on a specified
stack unit by entering the following commands on the master switch.
• Configure the PFC buffer for all switches in the stack.
CONFIGURATION mode
[no] dcb stack-unit all pfc-buffering pfc-port {1-64} pfc-queues {1-2}
By default, the PFC buffer is enabled on all ports on the stack unit.
• Configure the PFC buffer for all port pipes in a specified stack unit by specifying the port-pipe
number, number of PFC-enabled ports, and number of configured lossless queues.
CONFIGURATION mode
[no] dcb stack-unit stack-unit-id [port-set port-set-id] pfc-buffering pfc-
ports {1-64} pfc-queues {1-2}
Valid stack-unit IDs are 0 to 5.
The only valid port-set ID (port-pipe number) is 0.
Dell Networking OS Behavior: If you configure PFC on a 40GbE port, count the 40GbE port as four PFC-
enabled ports in the pfc-port number you enter in the command syntax.
To achieve lossless PFC operation, the PFC port count and queue number used for the reserved buffer
size that is created must be greater than or equal to the buffer size required for PFC-enabled ports and
lossless queues on the switch.
For the PFC buffer configuration to take effect, you must reload the stack or a specified stack unit (use
the reload command at EXEC Privilege level).
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Data Center Bridging (DCB)