Reference Guide

• 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.
If you configure a DCBx port to operate with a specific version (the DCBx version {cee | cin | ieee-
v2.5} command in the Configuring DCBx), DCBx operations are performed according to the configured version,
including fast and slow transmit timers and message formats. If a DCBx frame with a different version is received, a
syslog message is generated and the peer version is recorded in the peer status table. If the frame cannot be
processed, it is discarded and the discard counter is incremented.
NOTE: Because DCBx TLV processing is best effort, it is possible that CIN frames may be processed when DCBx is
configured to operate in CEE mode and vice versa. In this case, the unrecognized TLVs cause the unrecognized
TLV counter to increment, but the frame is processed and is not discarded.
Legacy DCBx (CIN and CEE) supports the DCBx control state machine that is defined to maintain the sequence number
and acknowledge the number sent in the DCBx control TLVs.
DCBx Example
The following figure shows how to use DCBx.
The external 40GbE ports on the base module (ports 33 and 37) of two switches are used for uplinks configured as DCBx
auto-upstream ports. The S4820T is connected to third-party, top-of-rack (ToR) switches through 40GbE uplinks. The ToR
switches are part of a Fibre Channel storage network.
The internal ports (ports 1-32) connected to the 10GbE backplane are configured as auto-downstream ports.
On the S4820T, PFC and ETS use DCBx to exchange link-level configuration with DCBx peer devices.
Figure 34. DCBx Sample Topology
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