Deployment Guide

The conguration of no-drop queues provides exibility for ports on which PFC is not needed but lossless trac should egress from the
interface.
Lossless trac egresses out the no-drop queues. Ingress dot1p trac from PFC-enabled interfaces is automatically mapped to the no-drop
egress queues.
1 Enter INTERFACE Conguration mode.
CONFIGURATION mode
interface type slot/port
2 Congure the port queues that still functions as no-drop queues for lossless trac.
INTERFACE mode
pfc no-drop queues queue-range
For the dot1p-queue assignments, refer to the dot1p Priority-Queue Assignment table.
The maximum number of lossless queues globally supported on the switch is four.
The range is from 0 to 3. Separate the queue values with a comma; specify a priority range with a dash; for example, pfc no-drop
queues 1,3 or pfc no-drop queues 2-3.
The default: No lossless queues are congured.
NOTE: Dell Networking OS Behavior: By default, no lossless queues are congured on a
port.
A limit of two lossless queues is supported on a port. If the amount of priority trac that you congure to be paused exceeds the two
lossless queues, an error message displays. Recongure the input policy using a smaller number of PFC priorities.
If you congure lossless queues on an interface that already has a DCB input policy with PFC enabled (pfc mode on), an error message
displays.
Trac may be interrupted due to an interface ap (going down and coming up) when you recongure lossless queues on no-drop priorities
in an input policy and re-apply the policy to an interface.
Conguring the PFC Buer in a Switch Stack
In a switch stack, you must congure all stacked ports with the same PFC conguration. In addition, you must congure a separate buer
of memory allocated exclusively to a service pool accessed by queues on which priority-based control ows are mapped.
These PFC-enabled queues ensure the lossless transmission of storage and server trac. The buer required for the PFC service pool is
calculated based on the number of ports and port queues used by PFC trac.
You can congure the size of the PFC buer for all switches in a stack or all port pipes on a specied stack unit by entering the following
commands on the master switch.
• Congure the PFC buer for all switches in the stack.
CONFIGURATION mode
[no] dcb stack-unit all pfc-buffering pfc-port {1-56} pfc-queues {1-2}
By default, the PFC buer is enabled on all ports on the stack unit.
• Congure the PFC buer for all port pipes in a specied stack unit by specifying the port-pipe number, number of PFC-enabled ports,
and number of congured lossless queues.
CONFIGURATION mode
[no] dcb stack-unit stack-unit-id [port-set port-set-id] pfc-buffering pfc-ports {1-56} pfc-
queues {1-2}
250
Data Center Bridging (DCB)