Dell S4048-ON - PFC Prerequisites and Restrictions; Applying a DCB Map on a Port

• To disable PFC operation on an interface, use the no pfc mode on command in DCB-Map conguration mode.
• Trac may be interrupted when you recongure PFC no-drop priorities in a DCB map or re-apply the DCB map to an interface.
• For PFC to be applied, the congured priority trac 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 ow control on the interface using the flowcontrol
rx on tx on command. To delete the DCB map, rst disable link-level ow control. PFC is then automatically enabled on the
interface because an interface is PFC-enabled by default.
• To ensure no-drop handling of lossless trac, PFC allows you to congure lossless queues on a port (see Conguring Lossless Queues).
• When you congure 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 ow control is already enabled on an interface. You cannot enable
PFC and link-level ow control at the same time on an interface.
• In a switch stack, congure all stacked ports with the same PFC conguration.
• Dell Networking OS allows you to change the default dot1p priority-queue assignments only if the change satises the following
requirements 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 reconguration 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 a switch, PFC is globally enabled by default, but not applied on specic 802.1p priorities. To enable PFC on 802.1p priorities, create a
DCB map.
The following prerequisites and restrictions apply when you congure PFC in a DCB map:
• You can enable PFC on a maximum of two priority queues on an interface. Enabling PFC for dot1p priorities congures the
corresponding port queue as lossless.
• You cannot enable PFC and link-level ow control at the same time on an interface.
Applying a DCB Map on a Port
When you apply a DCB map with PFC enabled on a switch interface, a memory buer for PFC-enabled priority trac is automatically
allocated. The buer 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 16. DCB Map to an Ethernet Port
Step Task Command Command Mode
1
Enter interface conguration mode on an Ethernet port.
interface
{tengigabitEthernet slot/
port [/subport] |
fortygigabitEthernetslot/
port}
CONFIGURATION
2
Apply the DCB map on the Ethernet port to congure it with
the PFC and ETS settings in the map; for example:
dcb-map name
INTERFACE
Data Center Bridging (DCB) 261