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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.
•
To disable PFC operation on an interface, use the
no pfc mode on
command in DCB-Map configuration mode.
•
Traffic may be interrupted when you reconfigure PFC no-drop priorities in a DCB map or re-apply the DCB map to an interface.
•
For PFC to be applied, the configured priority traffic must be supported by a PFC peer (as detected by DCBx).
•
If you apply a DCB map with PFC disabled (
pfc off
), you can enable link-level flow control on the interface using the
flowcontrol rx on tx on
command. To delete the DCB map, first disable link-level flow control. PFC is then
automatically enabled on the interface because an interface is PFC-enabled by default.
•
To ensure no-drop handling of lossless traffic, PFC allows you to configure lossless queues on a port (see
).
•
When you configure a DCB map, an error message is displayed if the PFC dot1p priorities result in more than two lossless queues.
•
When you apply a DCB map, an error message is displayed if link-level flow control is already enabled on an interface. You cannot
enable PFC and link-level flow control at the same time on an interface.
•
In a switch stack, configure all stacked ports with the same PFC configuration.
•
Dell Networking OS allows you to change the default dot1p priority-queue assignments only if the change satisfies the following
requirements in DCB maps already applied to S6000 interfaces:
•
All 802.1p priorities mapped to the same queue must be in the same priority group.
•
A maximum of two PFC-enabled, lossless queues are supported on an interface.
Otherwise, the reconfiguration of a default dot1p-queue assignment is rejected.
•
To ensure complete no-drop service, apply the same PFC parameters on all PFC-enabled peers.
PFC Prerequisites and Restrictions
On an S6000 switch, PFC is globally enabled by default, but not applied on specific 802.1p priorities. To enable PFC on 802.1p
priorities, create a DCB map.
The following prerequisites and restrictions apply when you configure PFC in a DCB map:
•
You can enable PFC on a maximum of two priority queues on an interface. Enabling PFC for dot1p priorities configures the
corresponding port queue as lossless.
•
You cannot enable PFC and link-level flow control at the same time on an interface.
Data Center Bridging (DCB)
249
Summary of Contents for S4048-ON
Page 1: ...Dell Configuration Guide for the S4048 ON System 9 9 0 0 ...
Page 146: ...Figure 14 BFD Three Way Handshake State Changes 146 Bidirectional Forwarding Detection BFD ...
Page 522: ...Figure 87 Configuring Interfaces for MSDP 522 Multicast Source Discovery Protocol MSDP ...
Page 523: ...Figure 88 Configuring OSPF and BGP for MSDP Multicast Source Discovery Protocol MSDP 523 ...
Page 528: ...Figure 91 MSDP Default Peer Scenario 1 528 Multicast Source Discovery Protocol MSDP ...
Page 529: ...Figure 92 MSDP Default Peer Scenario 2 Multicast Source Discovery Protocol MSDP 529 ...
Page 530: ...Figure 93 MSDP Default Peer Scenario 3 530 Multicast Source Discovery Protocol MSDP ...
Page 633: ...Policy based Routing PBR 633 ...
Page 777: ...Figure 119 Single and Double Tag TPID Match Service Provider Bridging 777 ...
Page 778: ...Figure 120 Single and Double Tag First byte TPID Match 778 Service Provider Bridging ...