Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.100.0 - Page 250

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 devices but do not accept or propagate internal or external configurations. Unlike other user-configured ports, the configuration of DCBx ports 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 are enabled. When making a configuration change to a DCBx port in a Manual role, Dell Networking recommends shutting down the interface using the shutdown command, change the configuration, then re-activate the interface using the no 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 the port. • 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 on the configuration-source port. When an application priority TLV is received on the configuration-source port, the auto-upstream and 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 configured PFC 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 the port. DCB Configuration Exchange The DCBx protocol supports the exchange and propagation of configuration information for the enhanced transmission selection (ETS) and priority-based flow control (PFC) DCB features. DCBx uses the following methods to exchange DCB configuration parameters: Asymmetric Symmetric DCB parameters are exchanged between a DCBx-enabled port and a peer port without requiring that a peer port and the local port use the same configured values for the configurations to be compatible. For example, ETS uses an asymmetric exchange of parameters between DCBx peers. DCB parameters are exchanged between a DCBx-enabled port and a peer port but requires that each configured parameter value be the same for the configurations in order to be compatible. For example, PFC uses an symmetric exchange of parameters between DCBx peers. 250 Data Center Bridging (DCB)