Configuring A Priority Flow Control Watchdog Interval - Cisco Nexus 9000 Series Configuration Manual

Configuring a Priority Flow Control Watchdog Interval

Command or Action
Step 20 priority-flow-control mode { auto | on | off }
Example:
switch(config-if)# priority-flow-control mode on
switch(config-if)#
Step 21
service-policy type qos input policy-name
Example:
switch(config-if)# service-policy type qos input
p1
Step 22
exit
Example:
switch(config-if)# exit
switch(config)#
Configuring a Priority Flow Control Watchdog Interval
A PFC storm may occur in the network from a malfunctioning NIC or switch, where the PFC frames are
propagated to all senders causing a complete stall in traffic in the network. To mitigate a PFC storm, a PFC
watchdog can be used. A PFC watchdog interval can be configure to detect whether packets in a no-drop
queue are being drained within a specified time period. If packets are present in buffer longer than the configured
time period and after the time period expires, all outgoing packets are dropped on the interfaces that match
the PFC queue that is not being drained.
Note PFC watchdog is not supported on Cisco Nexus 9500 platform switches with Cisco Nexus 9400, 9500 and
9600 line cards, with the exception of Cisco Nexus 9636PQ line cards (that support the PFC watchdog feature).
Note When the PFC watchdog is configured, the following behavior can occur:
After the watchdog timer is triggered, the system removes traffic from a non-drop queue and new incoming
traffic is not admitted in the ingress buffer. Any incoming traffic is dropped. This behavior may occur in cases
where drop and non-drop traffic are part of the same non-drop queue. It may also occur when the sender to
the non-drop queue is malfunctioning and still sends traffic even after a pause frame is received.
Note Ingress drops provide statistics of PFC watchdog dropped packets on the front panel ports.
Cisco Nexus 9000 Series NX-OS Quality of Service Configuration Guide, Release 7.x
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Purpose
Enables the priority flow control policy for the interface.
Adds classification to the interface ensuring that packets
matching the previously configured CoS or DSCP values
are classified in the correct QoS group.
Exits the ethernet interface mode and enters the global
configuration mode.
Configuring Priority Flow Control