• 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 using the flowcontrolrx on tx on command. To delete the DCB map, first disable link-level flow control. PFC is then automatically enabled on theinterface 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 Lossless Queues).• When you configure a DCB map, an error message is displayed if the PFC dot1p priorities result in more than two lossless queues.• When you apply a DCB map, an error message is displayed if link-level flow control is already enabled on an interface. You cannot enablePFC 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.• Dell Networking OS allows you to change the default dot1p priority-queue assignments only if the change satisfies the followingrequirements in DCB maps already applied to the 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 RestrictionsOn a switch, PFC is globally enabled by default, but not applied on specific 802.1p priorities. To enable PFC on 802.1p priorities, create aDCB map.The following prerequisites and restrictions apply when you configure PFC in a DCB map:• You can enable PFC on a maximum of four priority queues on an interface. The default is two. Enabling PFC for dot1p prioritiesconfigures the corresponding port queue as lossless.• You cannot enable PFC and link-level flow control at the same time on an interface.Applying a DCB Map on a PortWhen you apply a DCB map with PFC enabled on a switch interface, a memory buffer for PFC-enabled priority traffic is automaticallyallocated. The buffer size is allocated according to the number of PFC-enabled priorities in the assigned map.To apply a DCB map to an Ethernet port, follow these steps:Table 15. DCB Map to an Ethernet PortStep Task Command Command Mode1 Enter interface configuration mode on an Ethernet port. interface{tengigabitEthernet slot/port |fortygigabitEthernetslot/port}CONFIGURATION2 Apply the DCB map on the Ethernet port to configure it withthe PFC and ETS settings in the map; for example:dcb-map name INTERFACEData Center Bridging (DCB) 255
