Dell C1048P Port Extender Networking Configuration Guide for the C9000 Series - Page 292

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 autodownstream 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 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. Symmetric 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. Configuration Source Election When an auto-upstream or auto-downstream port receives a DCB configuration from a peer, the port first checks to see if there is an active configuration source on the switch. • If a configuration source already exists, the received peer configuration is checked against the local port configuration. If the received configuration is compatible, the DCBx marks the port as DCBxenabled. If the configuration received from the peer is not compatible, a warning message is logged 292 Data Center Bridging (DCB)