Setup Guide
Conguration Source Election
When an auto-upstream or auto-downstream port receives a DCB conguration from a peer, the port rst checks to see if there is an
active conguration source on the switch.
• If a conguration source already exists, the received peer conguration is checked against the local port conguration. If the received
conguration is compatible, the DCBx marks the port as DCBx-enabled. If the conguration received from the peer is not compatible, a
warning message is logged and the DCBx frame error counter is incremented. Although DCBx is operationally disabled, the port keeps
the peer link up and continues to exchange DCBx packets. If a compatible peer conguration is later received, DCBx is enabled on the
port.
• If there is no conguration source, a port may elect itself as the conguration source. A port may become the conguration source if
the following conditions exist:
– No other port is the conguration source.
– The port role is auto-upstream.
– The port is enabled with link up and DCBx enabled.
– The port has performed a DCBx exchange with a DCBx peer.
– The switch is capable of supporting the received DCB conguration values through either a symmetric or asymmetric parameter
exchange.
A newly elected conguration source propagates conguration changes received from a peer to the other auto-conguration ports. Ports
receiving auto-conguration information from the conguration source ignore their current settings and use the conguration source
information.
Propagation of DCB Information
When an auto-upstream or auto-downstream port receives a DCB conguration from a peer, the port acts as a DCBx client and checks if a
DCBx conguration source exists on the switch.
• If a conguration source is found, the received conguration is checked against the currently congured values that are internally
propagated by the conguration source. If the local conguration is compatible with the received conguration, the port is enabled for
DCBx operation and synchronization.
• If the conguration received from the peer is not compatible with the internally propagated conguration used by the conguration
source, the port is disabled as a client for DCBx operation and synchronization and a syslog error message is generated. The port keeps
the peer link up and continues to exchange DCBx packets. If a compatible conguration is later received from the peer, the port is
enabled for DCBx operation.
NOTE
: DCB congurations internally propagated from a conguration source do not overwrite the conguration on a DCBx port
in a manual role. When a conguration source is elected, all auto-upstream ports other than the conguration source are marked
as
willing disabled
. The internally propagated DCB conguration is refreshed on all auto-conguration ports and each port may
begin conguration negotiation with a DCBx peer again.
Auto-Detection and Manual Conguration of the DCBx Version
When operating in Auto-Detection mode (the DCBx version auto command), a DCBx port automatically detects the DCBx version on
a peer port. Legacy CIN and CEE versions are supported in addition to the standard IEEE version 2.5 DCBx.
A DCBx port detects a peer version after receiving a valid frame for that version. The local DCBx port recongures to operate with the peer
version and maintains the peer version on the link until one of the following conditions occurs:
• The switch reboots.
• The link is reset (goes down and up).
• User-congured CLI commands require the version negotiation to restart.
Data Center Bridging (DCB)
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