Reference Guide

294 | Data Center Bridging (DCB)
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DCBx Port Roles
To enable the auto-configuration of DCBx-enabled ports and propagate DCB configurations learned from
peer DCBx devices internally to other switch ports, use the following DCBx port roles:
• Auto-upstream: The port advertises its own configuration to DCBx peers and is
willing to receive peer
configuration. 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.
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.
• 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.
Note: When you configure the S5000 switch to operate as an NPIV proxy gateway (see NPIV Proxy
Gateway), DCBx supports only the manual port role.