Administrator Guide

The conguration received from a DCBx peer or from an internally propagated conguration is not stored in
the switch’s running conguration.
On a DCBx port in an auto-upstream role, the PFC and application priority TLVs are enabled. ETS
recommend TLVs are disabled and ETS conguration TLVs are enabled.
Auto-downstream The port advertises its own conguration to DCBx peers but is not willing to receive remote peer
conguration. The port always accepts internally propagated congurations from a conguration source. An
auto-downstream port that receives an internally propagated conguration overwrites its local conguration
with the new parameter values.
When an auto-downstream port receives and overwrites its conguration with internally propagated
information, one of the following actions is taken:
• If the peer conguration received is compatible with the internally propagated port conguration, the link
with the DCBx peer is enabled.
• If the received peer conguration is not compatible with the currently congured port conguration, the
link with the DCBx peer port is disabled and a syslog message for an incompatible conguration is
generated. The network administrator must then recongure the peer device so that it advertises a
compatible DCB conguration.
The internally propagated conguration is not stored in the switch’s running conguration. On a DCBx port in
an auto-downstream role, all PFC, application priority, ETS recommend, and ETS conguration TLVs are
enabled.
Default DCBx port role: Uplink ports are auto-congured in an auto-upstream role. Server-facing ports are auto-congured 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 congured PFC priorities on
the port.
• On auto-upstream and auto-downstream ports:
– If a conguration source is elected, the ports send an application priority TLV based on the application priority TLV
received on the conguration-source port. When an application priority TLV is received on the conguration-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 congured PFC priorities in application priority
TLVs.
– If no conguration source is congured, auto-upstream and auto-downstream ports check to see that the locally
congured 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
congured on the port.
DCB Conguration Exchange
On an Aggregator, the DCBx protocol supports the exchange and propagation of conguration information for the following DCB
features.
• Enhanced transmission selection (ETS)
• Priority-based ow control (PFC)
DCBx uses the following methods to exchange DCB conguration parameters:
Data Center Bridging (DCB)
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