Deployment Guide

dcbx port-role auto-downstream

no shutdown

Dell#

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

enabled.

Lossless Trac Handling In auto-DCB-enable mode, Aggregator ports operate with the auto-detection of DCBx trac. At any moment,

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

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

Lossless trac is not guaranteed when it is transmitted on a PFC-enabled port and received on a link-level ow control-enabled port, or

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

Enabling DCB on Next Reload To congure the Aggregator so that all interfaces come up with DCB enabled and ow control disabled, use

the dcb enable on-next-reload command. Internal PFC buers are automatically congured.

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

CONFIGURATION mode

dcb enable on-next-reload

To recongure the Aggregator so that all interfaces come up with DCB disabled and link-level ow control enabled, use the no dcb

enable on-next-reload

command. PFC buer memory is automatically freed.

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

with DCB disabled and ow 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 congure the Aggregator so that all interfaces are DCB enabled and ow control disabled, use the dcb enable

command.

Disabling DCB To congure the Aggregator so that all interfaces are DCB disabled and ow 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

Conguring Priority-Based Flow Control

PFC provides a ow control mechanism based on the 802.1p priorities in converged Ethernet trac received on an interface and is enabled

by default when you enable DCB.

As an enhancement to the existing Ethernet pause mechanism, PFC stops trac transmission for specied priorities (Class of Service

(CoS) values) without impacting other priority classes. Dierent trac types are assigned to dierent priority classes.

When trac congestion occurs, PFC sends a pause frame to a peer device with the CoS priority values of the trac 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) trac that requires no-drop service, while retaining

packet-drop congestion management for Local Area Network (LAN) trac.

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)