Data Center Bridging: Auto-Dcb-Enable Mode; When Dcb Is Disabled (Default) - Dell PowerEdge M IO Aggregator Command Reference Manual

Data Center Bridging: Auto-DCB-Enable Mode

On an Aggregator in standalone mode, the default mode of operation for data center bridging on Ethernet
ports is auto-DCB-enable mode. In this mode, Aggregator ports detect whether peer devices support
converged enhanced Ethernet (CEE) or not, and enable DCBX and PFC or link-level flow control
accordingly:
• Interfaces come up with DCB disabled and link-level flow control enabled to control data transmission
between the Aggregator and other network devices (see
When DCB is disabled on an interface, PFC, ETS, and DCBX are also disabled.
• When DCBX protocol packets are received, interfaces automatically enable DCB and disable
link-level flow control.
DCB is required for PFC, ETS, DCBX, and FCoE initialization protocol (FIP) snooping to operate.
Note: Normally, interfaces do not flap when DCB is automatically enabled.
DCB processes VLAN-tagged packets and dot1p priority values. Untagged packets are treated with a
dot1p priority of 0.
For DCB to operate effectively, ingress traffic is classified according to its dot1p priority so that it maps to
different data queues. The dot1p-queue assignments used on an Aggregator are shown in
dot1p Traffic Classification and Queue

When DCB is Disabled (Default)

By default, Aggregator interfaces operate with DCB disabled and link-level flow control enabled. When an
interface comes up, it is automatically configured with:
• Flow control enabled on input interfaces
• A DCB input policy with PFC disabled
• A DCB output policy with ETS disabled
Figure 6-4
When the first Aggregator interface with DCB disabled receives an LLDP packet with a DCBX TLV
advertisement, DCB is enabled on the interface and on all uplink interfaces.
56 | Data Center Bridging (DCB)
shows a default interface configuration with DCB enabled and link-level flow control enabled.
Flow Control Using Ethernet Pause
Assignment.
Frames).
Table 6-1 in QoS