Administrator Guide
Entering the no dcb-policy output stack-unit all command removes all DCB output policies applied to stacked ports.
The no dcb-policy output stack-unit stack-unit-id command removes only the DCB output policy applied to the
specied switch.
Congure a DCBx Operation
DCB devices use data center bridging exchange protocol (DCBx) to exchange conguration information with directly connected
peers using the link layer discovery protocol (LLDP) protocol.
DCBx can detect the misconguration of a peer DCB device, and optionally, congure peer DCB devices with DCB feature settings
to ensure consistent operation in a data center network.
DCBx is a prerequisite for using DCB features, such as priority-based ow control (PFC) and enhanced trac selection (ETS), to
exchange link-level congurations in a converged Ethernet environment. DCBx is also deployed in topologies that support lossless
operation for FCoE or iSCSI trac. In these scenarios, all network devices are DCBx-enabled (DCBx is enabled end-to-end). For
more information about how these features are implemented and used, refer to:
• Conguring Priority-Based Flow Control
• Congure Enhanced Transmission Selection
• Conguring FIP Snooping
DCBx supports the following versions: CIN, CEE, and IEEE2.5.
Prerequisite: For DCBx, enable LLDP on all DCB devices.
DCBx Operation
DCBx performs the following operations:
• Discovers DCB conguration (such as PFC and ETS) in a peer device.
• Detects DCB mis-conguration in a peer device; that is, when DCB features are not compatibly congured on a peer device and
the local switch. Mis-conguration detection is feature-specic because some DCB features support asymmetric conguration.
• Recongures a peer device with the DCB conguration from its conguration source if the peer device is willing to accept
conguration.
• Accepts the DCB conguration from a peer if a DCBx port is in “willing” mode to accept a peer’s DCB settings and then internally
propagates the received DCB conguration to its peer ports.
DCBx Port Roles
To enable the auto-conguration of DCBx-enabled ports and propagate DCB congurations learned from peer DCBx devices
internally to other switch ports, use the following DCBx port roles.
Auto-upstream
The port advertises its own conguration to DCBx peers and receives its conguration from DCBX peers
(ToR or FCF device). The port also propagates its conguration to other ports on the switch.
The rst auto-upstream that is capable of receiving a peer conguration is elected as the conguration
source. The elected conguration source then internally propagates the conguration to other auto-
upstream and auto-downstream ports. A port that receives an internally propagated conguration
overwrites its local conguration with the new parameter values.
When an auto-upstream port (besides the conguration source) receives and overwrites its conguration
with internally propagated information, one of the following actions is taken:
• If the peer conguration received is compatible with the internally propagated port conguration, the link
with the DCBx peer is enabled.
• If the received peer conguration is not compatible with the currently congured port conguration, the
link with the DCBX peer port is disabled and a syslog message for an incompatible conguration is
Data Center Bridging (DCB)
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