DELL N3000 User Manual

Configuring Data Center Bridging Features

To be interoperable with legacy industry implementations of the DCBx 

protocol, The Dell Networking N4000 switches use a hybrid model to support 

both the IEEE version of DCBx (IEEE 802.1Qaz) and legacy DCBx versions. 
The N4000 switch automatically detects whether a peer is operating with 

either of the two CEE DCBx versions or the IEEE standard DCBx version 

(the default mode). You can also configure DCBx to manually select one of 

the legacy versions or IEEE standard mode. In auto-detect mode, the switch 

starts operating in IEEE DCBx mode on a port, and if it detects a legacy 

DCBx device based on the OUI of the organization TLV, then the switch 

changes its DCBx mode on that port to support the version detected. There is 

no timeout mechanism to move back to IEEE mode. If the DCBx peer times 

out, multiple peers are detected, the link is reset (link down/up) or if 

commanded by the operator, DCBx resets its operational mode to IEEE.
The interaction between the DCBx component and other components 

remains the same irrespective of the operational mode it is executing. For 

instance, the DCBx component interacts with PFC to get needed 

information to pack the TLVs to be sent out on the interface. Based on the 

operational control mode of the port, DCBx packs it in the proper frame 

format.

The behavior of each port is dependent on its operational mode and that of 

other ports in the stack. The port mode is a DCBx configuration item that is 

passed to the DCBx clients to control the processing of their configuration 

information. There are four port roles:

1 Manual
2 Auto-Upstream
3 Auto-Downstream
4 Configuration Source

Ports operating in the manual role do not have their configuration affected by 

peer devices or by internal propagation of configuration. These ports have 

their operational mode, traffic classes, and bandwidth information specified