Users Guide

no shutdown

Dell#

When no DCBx TLVs are received on a DCB-enabled interface for 180 seconds, DCB is automatically disabled and flow control is re-

enabled.

Lossless Traffic Handling In auto-DCB-enable mode, Aggregator ports operate with the auto-detection of DCBx traffic. At any moment,

some ports may operate with link-level flow control while others operate with DCB-based PFC enabled.

As a result, lossless traffic is ensured only if traffic ingresses on a PFC-enabled port and egresses on another PFC-enabled port.

Lossless traffic is not guaranteed when it is transmitted on a PFC-enabled port and received on a link-level flow control-enabled port, or

transmitted on a link-level flow control-enabled port and received on a PFC-enabled port.

Enabling DCB on Next Reload To configure the Aggregator so that all interfaces come up with DCB enabled and flow control disabled,

use the dcb enable on-next-reload command. Internal PFC buffers are automatically configured.

1 Globally enable DCB on all interfaces after next switch reload.

CONFIGURATION mode

dcb enable on-next-reload

To reconfigure the Aggregator so that all interfaces come up with DCB disabled and link-level flow control enabled, use the no dcb

enable on-next-reload

command. PFC buffer memory is automatically freed.

Enabling Auto-DCB-Enable Mode on Next Reload To configure the Aggregator so that all interfaces come up in auto-DCB-enable mode

with DCB disabled and flow control enabled, use the dcb enable aut-detect on-next-reload command.

1 Globally enable auto-detection of DCBx and auto-enabling of DCB on all interfaces after switch reload.

CONFIGURATION mode

dcb enable auto-detect on-next-reload

Enabling DCB To configure the Aggregator so that all interfaces are DCB enabled and flow control disabled, use the dcb enable

command.

Disabling DCB To configure the Aggregator so that all interfaces are DCB disabled and flow control enabled, use the no dcb enable

command.

dcb enable auto-detect on-next-reload Command Example

Dell#dcb enable auto-detect on-next-reload

Configuring Priority-Based Flow Control

PFC provides a flow control mechanism based on the 802.1p priorities in converged Ethernet traffic received on an interface and is

enabled by default when you enable DCB.

As an enhancement to the existing Ethernet pause mechanism, PFC stops traffic transmission for specified priorities (Class of Service

(CoS) values) without impacting other priority classes. Different traffic types are assigned to different priority classes.

When traffic congestion occurs, PFC sends a pause frame to a peer device with the CoS priority values of the traffic that is to be stopped.

Data Center Bridging Exchange protocol (DCBx) provides the link-level exchange of PFC parameters between peer devices. PFC allows

network administrators to create zero-loss links for Storage Area Network (SAN) traffic that requires no-drop service, while retaining

packet-drop congestion management for Local Area Network (LAN) traffic.

To ensure complete no-drop service, apply the same DCB input policy with the same pause time and dot1p priorities on all PFC-enabled

peer interfaces.

Data Center Bridging (DCB)