Administrator Guide
EXEC mode
EXEC Privilege mode
show hardware pfc-nodrop-priority l2-dlf drops stack-unit stack-unit-number port-set port-
pipe
DellEMC#show hardware pfc-nodrop-priority l2-dlf drops stack-unit 0 port-set 0
---------------------------------------------------
Priority DropCount
---------------------------------------------------
0 0
1 0
2 0
3 0
4 0
5 0
6 0
7 0
To clear the drop statistics, use the clear hardware pfc-nodrop-priority l2-dlf drops stack-unit stack-
unit-number port-set port-pipe command.
NOTE:
Dell EMC Networking OS Behavior: By default, no lossless queues are configured on a port.
A limit of two lossless queues is supported on a port. If the amount of priority traffic that you configure to be paused exceeds the two
lossless queues, an error message displays.
In S6000, any pfc-dot1p priorities configured on a given interface need not be the same across the system. In other words, lossless queue
limit is applicable on a per-port level and not on the global-config context. For example, one of the interfaces can have pfc-dot1p priorities
as 2 and 3. Whereas, the other interface(s) can have its pfc-dot1p priorities as 4 and 5.
It is the user responsibility to have symmetric PFC configurations on the interfaces involved in a particular PFC-enabled traffic-flow to
obtain lossless behavior.
Configuring PFC in a DCB Map
A switch supports the use of a DCB map in which you configure priority-based flow control (PFC) setting. To configure PFC parameters,
you must apply a DCB map on an interface.
PFC Configuration Notes
PFC provides flow control based on the 802.1p priorities in a converged Ethernet traffic that is received on an interface and is enabled by
default when you enable DCB. As an enhancement to the existing Ethernet pause functionality, PFC stops traffic transmission for
specified priorities (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 needs to be
stopped. DCBx provides the link-level exchange of PFC parameters between peer devices. PFC allows network administrators to create
zero-loss links for SAN traffic that requires no-drop service, while at the same time retaining packet-drop congestion management for
LAN traffic.
On a switch, PFC is enabled by default on Ethernet ports (pfc mode on command). You can configure PFC parameters using a DCB
map or the pfc priority command in Interface configuration mode. For more information, see Configuring Priority-Based Flow
Control.
As soon as you apply a DCB map with PFC enabled on an interface, DCBx starts exchanging information with a peer. The IEEE802.1Qbb,
CEE and CIN versions of PFC TLV are supported. DCBx also validates PFC configurations that are received in TLVs from peer devices. By
applying a DCB map with PFC enabled, you enable PFC operations on ingress port traffic. To achieve complete lossless handling of traffic,
configure PFC priorities on all DCB egress ports.
When you apply or remove a DCB input policy from an interface, one or two CRC errors are expected to be noticed on the ingress ports
for each removal or attachment of the policy. This behavior occurs because the port is brought down when PFC is configured. When a
DCB input policy with PFC profile is configured or unconfigured on an interface or a range of interfaces not receiving any traffic,
interfaces with PFC settings that receive appropriate PFC-enabled traffic (unicast, mixed-frame-size traffic) display incremental values in
the CRC and discards counters. (These ingress interfaces receiving pfc-enabled traffic have an egress interface that has a compatible
PFC configuration).
NOTE:
DCB maps are supported only on physical Ethernet interfaces.
• To remove a DCB map, including the PFC configuration it contains, use the no dcb map command in Interface configuration mode.
Data Center Bridging (DCB)
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