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● 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.
Auto-
downstream
The port advertises its own configuration to DCBx peers but is not willing to receive remote peer
configuration. The port always accepts internally propagated configurations from a configuration source.
An auto-downstream port that receives an internally propagated configuration overwrites its local
configuration with the new parameter values.
When an auto-downstream port 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 internally propagated configuration is not stored in the switch's running configuration.
○ On a DCBx port in an auto-downstream role, all PFC, application priority, ETS recommend, and
ETS configuration TLVs are enabled.
Configuration
source
The port is configured to serve as a source of configuration information on the switch. Peer DCB
configurations received on the port are propagated to other DCBx auto-configured ports. If the peer
configuration is compatible with a port configuration, DCBx is enabled on the port.
On a configuration-source port, the link with a DCBx peer is enabled when the port receives a
DCB configuration that can be internally propagated to other auto-configured ports. The configuration
received from a DCBx peer is not stored in the switch’s running configuration. On a DCBx port that is the
configuration source, all PFC and application priority TLVs are enabled. ETS recommend TLVs are disabled
and ETS configuration TLVs are enabled.
Manual The port is configured to operate only with administrator-configured settings and does not auto-configure
with DCB settings received from a DCBx peer or from an internally propagated configuration from the
configuration source. If you enable DCBx, ports in Manual mode advertise their configurations to peer
Data Center Bridging (DCB) 247