Deployment Guide

• Data center bridging exchange protocol
• FCoE initialization protocol (FIP) snooping
DCB processes virtual local area network (VLAN)-tagged packets and dot1p priority values. Untagged packets are treated with a dot1p
priority of 0.
For DCB to operate eectively, you can classify ingress trac according to its dot1p priority so that it maps to dierent data queues. The
dot1p-queue assignments used are shown in the following table.
On the FN IOM Switch, by default, DCB is enabled and MMU buers are reserved to achieve no-drop trac handling for PFC. Disabling
DCB does not release the buers reserved by default. To utilize reserved buers for non-DCB applications, you have to explicitly release the
buers (Refer to Conguring the PFC Buer in a Switch Stack).
To disable or re-enable DCB on a switch, enter the following commands.
1 Disable DCB.
CONFIGURATION mode
no dcb enable
2 Re-enable DCB.
CONFIGURATION mode
dcb enable
NOTE: Dell Networking OS Behavior: DCB is not supported if you enable link-level ow control on one or more
interfaces.
After you disable DCB, if link-level ow control is not automatically enabled on an interface, to enable ow control, manually shut down the
interface (the shutdown command) and re-enable it (the no shutdown command).
QoS dot1p Trac Classication and Queue Assignment
The following section describes QoS dot1P trac classication and assignments.
DCB supports PFC, ETS, and DCBx to handle converged Ethernet trac that is assigned to an egress queue according to the following
QoS methods:
Honor dot1p
You can honor dot1p priorities in ingress trac at the port or global switch level (refer to Default dot1p to Queue
Mapping) using the service-class dynamic dot1p command in INTERFACE conguration mode (refer to
Honoring dot1p Values on Ingress Packets).
Layer 2 class maps You can use dot1p priorities to classify trac in a class map and apply a service policy to an ingress port to map
trac to egress queues (refer to Policy-Based QoS Congurations).
NOTE: Dell Networking does not recommend mapping all ingress trac to a single queue when using PFC and ETS. However,
Dell Networking does recommend using Ingress trac classication using the service-class dynamic dot1p command
(honor dot1p) on all DCB-enabled interfaces. If you use L2 class maps to map dot1p priority trac to egress queues, take into
account the default dot1p-queue assignments in the following table and the maximum number of two lossless queues supported
on a port (refer to Conguring Lossless Queues).
Although the system allows you to change the default dot1p priority-queue assignments (refer to Setting dot1p Priorities for Incoming
Trac), DCB policies applied to an interface may become invalid if you recongure dot1p-queue mapping. If the congured DCB policy
remains valid, the change in the dot1p-queue assignment is allowed. For DCB ETS enabled interfaces, trac destined to queue that is
not mapped to any dot1p priority are dropped.
FC Flex IO Modules 953