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 withthe DCBx peer is enabled.• If the received peer configuration is not compatible with the currently configured port configuration, the linkwith the DCBx peer port is disabled and a syslog message for an incompatible configuration is generated. Thenetwork administrator must then reconfigure the peer device so that it advertises a compatible DCBconfiguration.• 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 ETSconfiguration TLVs are enabled.Configuration source The port is configured to serve as a source of configuration information on the switch. Peer DCB configurationsreceived on the port are propagated to other DCBx auto-configured ports. If the peer configuration is compatiblewith 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 configurationthat can be internally propagated to other auto-configured ports. The configuration received from a DCBx peer isnot stored in the switch’s running configuration. On a DCBx port that is the configuration source, all PFC andapplication 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 withDCB settings received from a DCBx peer or from an internally propagated configuration from the configurationsource. If you enable DCBx, ports in Manual mode advertise their configurations to peer devices but do not acceptor propagate internal or external configurations. Unlike other user-configured ports, the configuration of DCBxports in Manual mode is saved in the running configuration.On a DCBx port in a manual role, all PFC, application priority, ETS recommend, and ETS configuration TLVs areenabled.When making a configuration change to a DCBx port in a Manual role, Dell Networking recommends shutting downthe interface using the shutdown command, change the configuration, then re-activate the interface using theno shutdown command.The default for the DCBx port role is manual.NOTE: On a DCBx port, application priority TLV advertisements are handled as follows:• The application priority TLV is transmitted only if the priorities in the advertisement match the configured PFC priorities on theport.• On auto-upstream and auto-downstream ports:• If a configuration source is elected, the ports send an application priority TLV based on the application priority TLV received onthe configuration-source port. When an application priority TLV is received on the configuration-source port, the auto-upstreamand auto-downstream ports use the internally propagated PFC priorities to match against the received application priority.Otherwise, these ports use their locally configured PFC priorities in application priority TLVs.• If no configuration source is configured, auto-upstream and auto-downstream ports check to see that the locally configuredPFC priorities match the priorities in a received application priority TLV.• On manual ports, an application priority TLV is advertised only if the priorities in the TLV match the PFC priorities configured on theport.DCB Configuration ExchangeThe DCBx protocol supports the exchange and propagation of configuration information for the enhanced transmission selection (ETS) andpriority-based flow control (PFC) DCB features.DCBx uses the following methods to exchange DCB configuration parameters:268 Data Center Bridging (DCB)
