Users Guide

On a conguration-source port, the link with a DCBx peer is enabled when the port receives a DCB
conguration that can be internally propagated to other auto-congured ports. The conguration received
from a DCBx peer is not stored in the switch’s running conguration. On a DCBx port that is the
conguration source, all PFC and application priority TLVs are enabled. ETS recommend TLVs are disabled
and ETS conguration TLVs are enabled.
Manual The port is congured to operate only with administrator-congured settings and does not auto-congure
with DCB settings received from a DCBx peer or from an internally propagated conguration from the
conguration source. If you enable DCBx, ports in Manual mode advertise their congurations to peer
devices but do not accept or propagate internal or external congurations. Unlike other user-congured
ports, the conguration of DCBx ports in Manual mode is saved in the running conguration.
On a DCBx port in a manual role, all PFC, application priority, ETS recommend, and ETS conguration TLVs
are enabled.
When making a conguration change to a DCBx port in a Manual role, Dell Networking recommends
shutting down the interface using the shutdown command, change the conguration, 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 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
The DCBx protocol supports the exchange and propagation of conguration information for the enhanced transmission selection
(ETS) and priority-based ow control (PFC) DCB features.
DCBx uses the following methods to exchange DCB conguration parameters:
Asymmetric
DCB parameters are exchanged between a DCBx-enabled port and a peer port without requiring that a peer
port and the local port use the same congured values for the congurations to be compatible. For example,
ETS uses an asymmetric exchange of parameters between DCBx peers.
Symmetric DCB parameters are exchanged between a DCBx-enabled port and a peer port but requires that each
congured parameter value be the same for the congurations in order to be compatible. For example, PFC
uses an symmetric exchange of parameters between DCBx peers.
Conguration Source Election
When an auto-upstream or auto-downstream port receives a DCB conguration from a peer, the port rst checks to see if there is
an active conguration source on the switch.
• If a conguration source already exists, the received peer conguration is checked against the local port conguration. If the
received conguration is compatible, the DCBx marks the port as DCBx-enabled. If the conguration received from the peer is
not compatible, a warning message is logged and the DCBx frame error counter is incremented. Although DCBx is operationally
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Data Center Bridging (DCB)