Reference Guide

Data Center Bridging (DCB) | 297
Auto-Detection and Manual Configuration of the DCBx Version
When operating in Auto-Detection mode (DCBx version auto command in the DCBx Configuration
Procedure), 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.
If you configure a DCBx port to operate with a specific version (
DCBx version {cee | cin | ieee-v2.5}
command in the DCBx Configuration Procedure), 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.
Legacy DCBx (CIN and CEE) supports the DCBx control state machine that is defined to maintain the
sequence number and acknowledge number sent in the DCBx control TLVs.
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 be incremented, but the frame is processed and is not discarded.