Dell PowerEdge FX2/FX2s - Manual (Page 40)

DCBx Operation
DCBx performs the following operations:
• 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
The following DCBX port roles are auto-configured on an Aggregator to propagate DCB configurations
learned from peer DCBX devices internally to other switch ports:
Auto-upstream The port advertises its own configuration to DCBx peers and receives its
configuration from DCBX peers (ToR or FCF device). 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.
40 Data Center Bridging (DCB)