Reference Guide

294 | Data Center Bridging (DCB)
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• 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.
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 Force10 recommends
that you shut down the interface using the
shutdown command, change the configuration, then
re-activate the interface using the
no shutdown command.
Default DCBx port role: 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.