Administrator Guide

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, consider the following points:
• By default, no lossless queues are configured on a port.
• A limit of 4 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 is displayed. You must re-configure 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 is displayed.
Table 18. Configuring Lossless Queues
Step Task Command Command Mode
1 Enter INTERFACE Configuration
mode.
interface
{tengigabitEthernet
slot/port |
fortygigabitEthernet
slot}
port-number is a port number
from 0 to 23.
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 the PFC operation, on
the interface
dcb-map {name }
INTERFACE
6
Configure the port queues that
still function as no-drop queues
for lossless traffic. For the
dot1p-queue assignments.
The maximum number of
lossless queues globally
supported on a port is 2.
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
queuesqueue-range
INTERFACE
242 Data Center Bridging (DCB)