Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.100.0 - Page 252
DCBx Example, DCBx Prerequisites and Restrictions
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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 40GbE ports on the base module (ports 33 and 37) of two switches are used for uplinks configured as DCBx autoupstream ports. The device 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 31. DCBx Sample Topology DCBx Prerequisites and Restrictions The following prerequisites and restrictions apply when you configure DCBx operation on a port: • For DCBx, on a port interface, enable LLDP in both Send (TX) and Receive (RX) mode (the protocol lldp mode command; refer to the example in CONFIGURATION versus INTERFACE Configurations in the Link Layer Discovery Protocol (LLDP) chapter). If multiple DCBx peer ports are detected on a local DCBx interface, LLDP is shut down. • The CIN version of DCBx supports only PFC, ETS, and FCOE; it does not support iSCSI, backward congestion management (BCN), logical link down (LLDF), and network interface virtualization (NIV). 252 Data Center Bridging (DCB)
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