Dell PowerEdge FX2/FX2s - Manual (Page 41)

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.
Default DCBX port role: Uplink ports are auto-configured in an auto-upstream role. Server-facing ports
are auto-configured in an auto-downstream role.
NOTE: You can change the port roles only in the PMUX mode. Use the following command to
change the port roles:
dcbx port-role {auto-downstream | auto-upstream | config-source | manual}
manual is the default port role.
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
On an Aggregator, the DCBX protocol supports the exchange and propagation of configuration
information for the following DCB features.
• Enhanced transmission selection (ETS)
• Priority-based flow control (PFC)
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
Data Center Bridging (DCB) 41