Auto-Detection and Manual Configuration of the DCBx VersionWhen operating in Auto-Detection mode (the DCBx version auto command), a DCBx port automatically detects the DCBx version ona 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 peerversion 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 (the DCBx version {cee | cin | ieee-v2.5} command in theConfiguring DCBx), DCBx operations are performed according to the configured version, including fast and slow transmit timers andmessage formats. If a DCBx frame with a different version is received, a syslog message is generated and the peer version is recorded inthe 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 tooperate in CEE mode and vice versa. In this case, the unrecognized TLVs cause the unrecognized TLV counter to increment, butthe 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 acknowledgethe number sent in the DCBx control TLVs.DCBx ExampleThe 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-upstreamports. The device is connected to third-party, top-of-rack (ToR) switches through uplinks. The ToR switches are part of a Fibre Channelstorage network.The internal ports (ports 1-32) connected to the 10GbE backplane are configured as auto-downstream ports.270 Data Center Bridging (DCB)
