Dell S4048T-ON, Configuration Manual

Page: 261 / 1146

• 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 flowcontrol
rx on tx on
command. 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 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 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.
• Dell Networking OS allows you to change the default dot1p priority-queue assignments only if the change satisfies 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 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 a 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.
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.
• You cannot enable PFC and link-level flow 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 buffer for PFC-enabled priority traffic is automatically
allocated. 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 16. DCB Map to an Ethernet Port
Step Task Command Command Mode
1
Enter interface configuration mode on an Ethernet port.
interface
{tengigabitEthernet
slot /
port [ /subport ] |
fortygigabitEthernet slot /
port
}
CONFIGURATION
2
Apply the DCB map on the Ethernet port to configure it with
the PFC and ETS settings in the map; for example:
dcb-map name
INTERFACE
Data Center Bridging (DCB) 261