Administrator Guide

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 requires.
NOTE: You cannot enable PFC and link-level ow control at the same time on an interface.
The Dell Networking OS does not support MACsec Bypass Capability (MBC).
Conguring Lossless Queues
DCB also supports the manual conguration of lossless queues on an interface when PFC mode is turned o and priority classes are
disabled in a DCB input policy applied to the interface.
Prerequisite: A DCB input policy 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).
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 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 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.
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Data Center Bridging (DCB)