Reference Guide

290 | Data Center Bridging (DCB)
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Configuring Lossless Queues
DCB also supports the manual configuration of lossless queues on an interface after you disable PFC mode
in a DCB map and apply the map on 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 802.1p traffic from PFC-enabled peers is
automatically mapped to the no-drop egress queues.
When configuring lossless queues on a port interface, take into account:
• By default, no lossless queues are configured on a port.
• A limit of two lossless queues are supported on a port. If the number of lossless queues configured
exceeds the maximum supported limit per port (two), an error message displays. You must reconfigure
the value to a smaller number of queues.
• If you configure lossless queues on an interface that already has a DCB map with PFC enabled (pfc
on), an error message displays.
Step Task Command Command Mode
1 Enter INTERFACE Configuration mode.
interface
{tengigabitEthernet slot/
port | fortygigabitEthernet
slot
/port}
CONFIGURATION
2 Open a DCB map and enter DCB map configuration
mode.
dcb-map name INTERFACE
3 Disable PFC.
no pfc mode on
DCB MAP
4 Return to interface configuration mode.
exit
DCB MAP
5 Apply the DCB map created to disable PFC
operation on the interface
dcb-map {name | default}
INTERFACE
6 Configure the port queues that still function as
no-drop queues for lossless traffic. For the
dot1p-queue assignments, see Table 13-1.
The maximum number of lossless queues globally
supported on a port is 2.
Note: You cannot configure PFC no-drop queues on
an interface on which a DCB map with PFC enabled
has been applied or which is already configured for
PFC using the pfc priority command.
Range: 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