Data Center Bridging: Default Configuration - Dell S4820T Configuration Manual

Important Points to Remember
• If you remove a dot1p priority-to-priority group mapping from a DCB map (no priority pgid
command), the PFC and ETS parameters revert to their default values on the interfaces on which the
DCB map is applied. By default, PFC is not applied on specific 802.1p priorities; ETS assigns equal
bandwidth to each 802.1p priority.
As a result, PFC and lossless port queues are disabled on 802.1p priorities, and all priorities are
mapped to the same priority queue and equally share the port bandwidth.
• To change the ETS bandwidth allocation configured for a priority group in a DCB map, do not modify
the existing DCB map configuration. Instead, first create a new DCB map with the desired PFC and
ETS settings, and apply the new map to the interfaces to override the previous DCB map settings.
Then, delete the original dot1p priority-priority group mapping.
If you delete the dot1p priority-priority group mapping (no priority pgid command) before you
apply the new DCB map, the default PFC and ETS parameters are applied on the interfaces. This
change may create a DCB mismatch with peer DCB devices and interrupt network operation.

Data Center Bridging: Default Configuration

Before you configure PFC and ETS on a switch see the priority group setting taken into account the
following default settings:
DCB is enabled.
PFC and ETS are globally enabled by default.
The default dot1p priority-queue assignments are applied as follows:
NOTE: Although, each port on the S4810, S4820T, and S5000 devices support 8 QoS queues, you
can configure only 4 QoS queues (0-3) to manage data traffic. The remaining 4 queues (4-7) are
reserved for control traffic.
NOTE: In Egress queue assignment (8 queues in S6000 and Z9500, 4 against in S5000 and S4810.
PFC is not applied on specific dot1p priorities.
ETS: Equal bandwidth is assigned to each port queue and each dot1p priority in a priority group.
To configure PFC and ETS parameters on an S6000 interface, you must specify the PFC mode, the ETS
bandwidth allocation for a priority group, and the 802.1p priority-to-priority group mapping in a DCB
map. No default PFC and ETS settings are applied to Ethernet interfaces.
Data Center Bridging (DCB)
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