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EX4550 Switches

Hierarchy Level


Configure a congestion notification profile (CNP) to enable priority-based flow control (PFC) on traffic and apply the profile to an interface. You can apply a CNP to most interfaces, including aggregated ethernet (AE) interfaces and their individual members.

A congestion notification profile can be configured to enable PFC on incoming traffic (input stanza) that matches the following:

  • A Differentiated Services code point (DSCP) value in the Layer 3 IP header (for traffic that is not VLAN-tagged).

  • An IEEE 802.1 code point at Layer 2 in the VLAN header (for VLAN-tagged traffic).

A congestion notification profile can be configured to enable PFC on outgoing traffic (output stanza) specified only by an IEEE 802.1 code point at Layer 2 in the VLAN header.


You must configure PFC for FCoE traffic. Each interface that carries FCoE traffic should be configured for PFC on the FCoE code point (usually 011).

There is no limit to the total number of congestion notification profiles you can create. However:

  • You can attach a maximum of one congestion notification profile to an interface.

  • DSCP-based PFC and IEEE 802.1p PFC cannot be configured under the same congestion notification profile.


Configuring or changing PFC on an interface blocks the entire port until the PFC change is completed. After a PFC change is completed, the port is unblocked and traffic resumes. Blocking the port stops ingress and egress traffic, and causes packet loss on all queues on the port until the port is unblocked.



Name of the congestion notification profile.


Enable the Priority Flow Control (PFC) watchdog. If you do not configure any options, the default values are used.

  • detection number of polling intervals—How many polling intervals the PFC watchdog waits before it determines that a PFC queue has stalled.

    • Default: 2

    • Range: 2-10

  • poll-interval time—How often the PFC watchdog checks the status of PFC queues. Configure the polling interval in milliseconds.

    • Default: 100

    • Range: 100-1000

  • recovery time—Configure in milliseconds how long the PFC watchdog disables the affected queues before it re-enables PFC.

    • Default: 200

    • Range: 200-10,000

  • watchdog-action drop—When the PFC watchdog detects that a PFC queue has stalled, it drops all queued packets and all newly arriving packets for the stalled PFC queue. This option is the default.

The remaining statements are explained separately. Search for a statement in CLI Explorer or click a linked statement in the Syntax section for details.

Required Privilege Level

interface—To view this statement in the configuration.interface-control—To add this statement to the configuration.

Release Information

Statement introduced in Junos OS Release 10.4.

Support for DSCP values introduced in Junos OS Release 17.4R1 for the QFX Series.

pfc-watchdog option introduced in Junos OS Evolved Release 20.4R1.