Concept Guide

● Apply the specified DCB policy on all ports of the switch stack or a single stacked switch.
CONFIGURATION mode
dcb-map {stack-unit all | stack-ports all} dcb-map-name
Configure a DCBx Operation
DCB devices use data center bridging exchange protocol (DCBx) to exchange configuration information with directly connected
peers using the link layer discovery protocol (LLDP) protocol.
DCBx can detect the misconfiguration of a peer DCB device, and optionally, configure 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 flow control (PFC) and enhanced traffic selection
(ETS), to exchange link-level configurations in a converged Ethernet environment. DCBx is also deployed in topologies that
support lossless operation for FCoE or iSCSI traffic. 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:
● Configure Enhanced Transmission Selection
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 configuration (such as PFC and ETS) in a peer device.
● Detects DCB mis-configuration in a peer device; that is, when DCB features are not compatibly configured on a peer
device and the local switch. Mis-configuration detection is feature-specific because some DCB features support asymmetric
configuration.
● Reconfigures a peer device with the DCB configuration from its configuration source if the peer device is willing to accept
configuration.
● Accepts the DCB configuration 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 configuration to its peer ports.
DCBx Port Roles
To enable the auto-configuration of DCBx-enabled ports and propagate DCB configurations learned from peer DCBx devices
internally to other switch ports, use the following DCBx port roles.
Auto-upstream
The port advertises its own configuration to DCBx peers and is willing to receive peer configuration. The
port also propagates its configuration to other ports on the switch.
The first auto-upstream that is capable of receiving a peer configuration is elected as the configuration
source. The elected configuration source then internally propagates the configuration to other auto-
upstream and auto-downstream ports. A port that receives an internally propagated configuration
overwrites its local configuration with the new parameter values. When an auto-upstream port (besides
the configuration source) receives and overwrites its configuration with internally propagated information,
one of the following actions is taken:
● If the peer configuration received is compatible with the internally propagated port configuration, the
link with the DCBx peer is enabled.
● If the received peer configuration is not compatible with the currently configured port configuration,
the link with the DCBx peer port is disabled and a syslog message for an incompatible configuration
is generated. The network administrator must then reconfigure the peer device so that it advertises a
compatible DCB configuration.
○ The configuration received from a DCBx peer or from an internally propagated configuration is not
stored in the switch’s running configuration.
○ On a DCBx port in an auto-upstream role, the PFC and application priority TLVs are enabled. ETS
recommend TLVs are disabled and ETS configuration TLVs are enabled.
268 Data Center Bridging (DCB)