Addendum

NOTE: DCB maps are supported only on physical Ethernet interfaces.
When you configure PFC in a DCB map:
• As soon as you apply a DCB map with PFC enabled on an interface, DCBx starts exchanging
information with a peer. The IEEE802.1Qbb, CEE and CIN versions of PFC TLV are supported. DCBx
also validates PFC configurations that are received in TLVs from peer devices.
By applying a DCB map with PFC enabled, you enable PFC operation on ingress port traffic. To achieve
complete lossless handling of traffic, configure PFC priorities on all DCB egress ports.
• To remove a DCB map, including the PFC configuration it contains, use the no dcb map command in
Interface configuration mode.
• To disable PFC operation on an interface, use the no pfc mode on command in DCB-Map
configuration mode.
• Traffic may be interrupted when you reconfigure PFC no-drop priorities in a DCB map or re-apply the
DCB map to an interface.
• For PFC to be applied, the configured priority traffic must be supported by a PFC peer (as detected by
DCBx).
• If you apply a DCB map with PFC disabled (pfc off):
• You can enable link-level flow control on the interface (flowcontrol rx on tx on command; see Using
Ethernet Pause Frames for Flow Control). To delete the DCB map, first disable link-level flow control.
PFC is then automatically enabled on the interface because an interface is PFC-enabled by default.
• To ensure no-drop handling of lossless traffic, PFC allows you to configure lossless queues on a port
(see Configuring DCB Maps and its Attributes).
• When you configure a DCB map, an error message displays if:
• The PFC dot1p priorities result in more than two lossless queues.
• When you apply a DCB map, an error message displays if:
• Link-level flow control is already enabled on an interface. You cannot enable PFC and link-level flow
control at the same time on an interface.
• In a switch stack, configure all stacked ports with the same PFC configuration.
• FTOS allows you to change the default dot1p priority-queue assignments only if the change satisfies
the following requirements in DCB maps already applied to S6000 interfaces:
• All 802.1p priorities mapped to the same queue must be in the same priority group.
• A maximum of two PFC-enabled, lossless queues are supported on an interface.
Otherwise the reconfiguration of a default dot1p-queue assignment is rejected.
• To ensure complete no-drop service, apply the same PFC parameters on all PFC-enabled peers.
PFC Prerequisites and Restrictions
On an S6000 switch, PFC is globally enabled by default, but not applied on specific 802.1p priorities. To
enable PFC on 802.1p priorities, create a DCB map. For more information, see Configuring DCB Maps
and its Attributes.
The following prerequisites and restrictions apply when you configure PFC in a DCB map:
• You can enable PFC on a maximum of two priority queues on an interface. Enabling PFC for dot1p
priorities configures the corresponding port queue as lossless.
Data Center Bridging (DCB)
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