Data Center Bridging (DCB) | 123
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:
Task Command Command Mode
Configure the PFC buffer for all switches
in the stack.
Default: The PFC buffer is enabled on all
ports on the stack unit.
[no] dcb stack-unit all pfc-buffering
pfc-port-count
{1-56} pfc-queues {1-2}
CONFIGURATION
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.
Valid stack-unit IDs are 0 to 5.
The only valid port-set ID (port-pipe
number) on an MXL Switch is 0.
[no] dcb stack-unit stack-unit-id
[port-set port-set-id] pfc-buffering
pfc-ports
{1-56} pfc-queues {1-2}
CONFIGURATION
FTOS 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
(reload command at the EXEC Privilege level).
If you configure the PFC buffer on all stack units, delete the startup configuration on both the master
and standby, and reload the stack, the new master (previously standby) generates the following syslog
message for each stack unit when it boots up:
PFC_BUFFER_CONFIG_CHANGED is generated for all stack units.
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