122 | Data Center Bridging (DCB)
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Configuring Lossless Queues
DCB also supports the manual configuration of lossless queues on an interface when PFC mode is turned
off and priority classes are disabled in a DCB input policy applied to the interface. The configuration of
no-drop queues provides flexibility for ports on which PFC is not needed but lossless traffic should egress
from the interface.
Lossless traffic egresses out the no-drop queues. Ingress dot1p traffic from PFC-enabled interfaces is
automatically mapped to the no-drop egress queues.
Prerequisite: A DCB input policy with PFC configuration is applied to the interface with the following
conditions:
• PFC mode is off (
no pfc mode on).
• No PFC priority classes are configured (
no pfc priority priority-range).
To configure lossless queues on a port interface, follow these steps:
Step Task Command Command Mode
1 Enter INTERFACE Configuration mode.
interface type slot/port
CONFIGURATION
2 Configure the port queues that will still function as
no-drop queues for lossless traffic. For the
dot1p-queue assignments, refer to Table 8-1.
Maximum number of lossless queues globally
supported on the switch: 2.
Valid values: 0-3. Separate 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
Default: No lossless queues are configured.
pfc no-drop queues
queue-range
INTERFACE
FTOS Behavior:
By default, no lossless queues are configured on a port.
A limit of two lossless queues are supported on a port. If the amount of priority traffic that you configure
to be paused exceeds the two lossless queues, an error message is displayed. You must reconfigure
the input policy using a smaller number of PFC priorities.
If you configure lossless queues on an interface that already has a DCB input policy with PFC enabled
(pfc mode on), an error message is displayed.
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.
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