Reference Guide

Applying DCB Policies on SFM Ports
To apply DCP configuration on SFM ports, follow these steps.
Configure DCB-MAP on backplane ports in both leaf and spine.
CONFIGURATION Mode
dcb-map sfm all backplane all dcb-map-name
The default is none.
If you apply a DCB Map with PFC disabled (no pfc mode on):
● You can enable link-level flow control on the interface (refer to Using Ethernet Pause Frames). To delete the input policy,
first disable link-level flow control. PFC is then automatically enabled on the interface because an interface is by default
PFC-enabled.
● PFC still allows you to configure lossless queues on a port to ensure no-drop handling of lossless traffic (refer to Configuring
Lossless Queues).
Configure a DCBx Operation
DCB devices use data center bridging exchange protocol (DCBx) to exchange configuration information with directly connected
peers using the link layer discovery protocol (LLDP) protocol.
DCBx can detect the misconfiguration of a peer DCB device, and optionally, configure peer DCB devices with DCB feature
settings to ensure consistent operation in a data center network.
DCBx is a prerequisite for using DCB features, such as priority-based flow control (PFC) and enhanced traffic selection (ETS),
to exchange link-level configurations in a converged Ethernet environment. DCBx is also deployed in topologies that support
lossless operation for FCoE or iSCSI traffic. In these scenarios, all network devices are DCBx-enabled (DCBx is enabled end-to-
end). For more information about how these features are implemented and used, refer to:
● Configure Enhanced Transmission Selection
DCBx supports the following versions: CIN, CEE, and IEEE2.5.
Prerequisite: For DCBx, enable LLDP on all DCB devices.
DCBx Operation
DCBx performs the following operations:
● Discovers DCB configuration (such as PFC and ETS) in a peer device.
● Detects DCB mis-configuration in a peer device; that is, when DCB features are not compatibly configured on a peer device
and the local switch. Mis-configuration detection is feature-specific because some DCB features support asymmetric
configuration.
● Reconfigures a peer device with the DCB configuration from its configuration source if the peer device is willing to accept
configuration.
● Accepts the DCB configuration from a peer if a DCBx port is in “willing” mode to accept a peer’s DCB settings and then
internally propagates the received DCB configuration to its peer ports.
DCBx Port Roles
To enable the auto-configuration of DCBx-enabled ports and propagate DCB configurations learned from peer DCBx devices
internally to other switch ports, use the following DCBx port roles.
Auto-upstream
The port advertises its own configuration to DCBx peers and is willing to receive peer configuration. The
port also propagates its configuration to other ports on the switch.
The first auto-upstream that is capable of receiving a peer configuration is elected as the configuration
source. The elected configuration source then internally propagates the configuration to other auto-
upstream and auto-downstream ports. A port that receives an internally propagated configuration
216 Data Center Bridging (DCB)