Users Guide

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.
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:
Data Center Bridging (DCB)
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