Reference Guide

Data Center Bridging (DCB) | 293
• Configuring Enhanced Transmission Selection
• FIP Snooping
• Chapter 13, Data Center Bridging (DCB)
The following versions of DCBx are supported CIN, CEE, and IEEE2.5.
Prerequisite: DCBx requires the LLDP to be enabled 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
Use the following 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:
• 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.