Install Guide

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 EMC Networking recommends
shutting down the interface using the shutdown command, change the configuration, then re-activate
the interface using the no shutdown command.
The default for the DCBx port role is 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.
DCB Configuration Exchange
The DCBx protocol supports the exchange and propagation of configuration information for the enhanced transmission selection
(ETS) and priority-based flow control (PFC) DCB features.
DCBx uses the following methods to exchange DCB configuration parameters:
Data Center Bridging (DCB)
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