Dell S4820T, Configuration Manual

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keeps the peer link up and continues to exchange DCBx packets. If a compatible peer configuration is
later received, DCBx is enabled on the port.
• If there is no configuration source, a port may elect itself as the configuration source. A port may
become the configuration source if the following conditions exist:
– No other port is the configuration 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 configuration values through either a
symmetric or asymmetric parameter exchange.
A newly elected configuration source propagates configuration changes received from a peer to the
other auto-configuration ports. Ports receiving auto-configuration information from the configuration
source ignore their current settings and use the configuration source information.
Propagation of DCB Information
When an auto-upstream or auto-downstream port receives a DCB configuration from a peer, the port
acts as a DCBx client and checks if a DCBx configuration source exists on the switch.
• If a configuration source is found, the received configuration is checked against the currently
configured values that are internally propagated by the configuration source. If the local configuration
is compatible with the received configuration, the port is enabled for DCBx operation and
synchronization.
• If the configuration received from the peer is not compatible with the internally propagated
configuration used by the configuration 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 configuration is later received from the peer,
the port is enabled for DCBx operation.
NOTE: DCB configurations internally propagated from a configuration source do not overwrite the
configuration on a DCBx port in a manual role. When a configuration source is elected, all auto-
upstream ports other than the configuration source are marked as
willing disabled . The internally
propagated DCB configuration is refreshed on all auto-configuration ports and each port may begin
configuration negotiation with a DCBx peer again.
Auto-Detection and Manual Configuration 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
reconfigures 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-configured CLI commands require the version negotiation to restart.
• The peer times out.
• Multiple peers are detected on the link.
Data Center Bridging (DCB)
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