Users Guide

• 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 14. 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 |
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:
Dell# interface tengigabitEthernet 1/1
Dell(config-if-te-1/1)# dcb-map
SAN_A_dcb_map1 Repeat Steps 1 and 2 to apply a DCB map
to more than one port.
You cannot apply a DCB map on an interface that has been
already congured for PFC using thepfc priority
command or which is already congured for lossless queues
(pfc no-drop queues command).
dcb-map name
INTERFACE
Data Center Bridging (DCB) 239