Setup Guide

NOTE: You cannot enable PFC and link-level ow control at the same time on an interface.
Conguring Lossless Queues
DCB also supports the manual conguration of lossless queues on an interface when PFC mode is turned o.
Prerequisite: A DCB with PFC conguration is applied to the interface with the following conditions:
• PFC mode is o (no pfc mode on).
• No PFC priority classes are congured (no pfc priority priority-range).
Example:
Port A —> Port B
Port C —> Port B
PFC no-drop queues are congured for queues 3, 4 on Port B. PFC capability is enabled on priorities 3, 4 on PORT A and C.
Port B acting as Egress
During the congestion, [trac pump on priorities 3 and 4 from PORT A and PORT C is at full line rate], PORT A and C send out the PFCs
to rate the trac limit. Egress drops are not observed on Port B since trac ow on priorities is mapped to loss less queues.
Port B acting as Ingress
If the trac congestion is on PORT B , Egress DROP is on PORT A or C, as the PFC is not enabled on PORT B.
Refer the following conguration for queue to dot1p mapping:
DellEMC(conf)#do show qos dot1p-queue-mapping
Dot1p Priority : 0 1 2 3 4 5 6 7
Queue : 2 0 1 3 4 5 6 7
DellEMC(conf)#
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 interface-type
2 Congure the port queues that will still function 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 two.
The range is from 0 to 7. Separate the queue values with a comma; specify a priority range with a dash; for example, pfc no-drop
queues 1,7 or pfc no-drop queues 2-7.
The default: No lossless queues are congured.
3 Congure to drop the unknown unicast packets ooding on lossless priorities.
Data Center Bridging (DCB)
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