Service Manual

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 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.
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 17. 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)
283