Users Guide

Detect PFC Storm
The following section explains the procedure to detect the PFC storm.
You can detect the PFC storm by polling the lossless queues in a port or priority periodically. When the queue depth is not equal to zero or
when the queue has trac after subsequent number of polling, then the port or priority is detected to have the PFC storm.
• Use the polling—interval {interval in milli-seconds} command to set the polling interval. The queue trac and
egress counters are polled.
• Use the xoff-state threshold polling-count {number of polling-interval} command to set the number of
times the polling should be done. If the trac and the egress counter remain the same after the subsequent polling, then the
corresponding port or priority is detected to have PFC storm.
• Once PFC storm is detected on an interface, you can use the storm-control pfc in queue-drop command on the interface
to drop the ingress packets. This command triggers a queue drop state on the interface with PFC storm, so that the trac through
other ports and priorities are not aected.
For more information about the above commands, see the Dell Networking OS Command Line Reference Guide.
Restore Queue Drop State
You can restore the queue drop triggered due to the storm control PFC detection to the normal state.
Once the storm control PFC is detected on a port or priority, you can activate the queue drop action. You can restore the dropped queue to
normal state on the following conditions.
• You can restore the queue after a particular period of time. Use the queue-drop backoff-force polling—count command to
remove the queue-drop state after the specied number of polling is done. The queue-drop state, which has been activated due to the
detection of storm control PFC, is forced to get removed. When the
number of polling-interval is set as ‘zero’, the queue-drop state is
not removed until it is explicitly cleared using the storm-control pfc in queue-drop-state clear command.
• You can restore the queue when additional PFC packets for a particular priority are not received for a specied period of time. Use the
queue-drop backoff-on-norxpfc polling-count command to remove the queue-drop state if additional PFCs are not
received after the specied number of polling is done.
For more information about the above commands, see the Dell Networking OS Command Line Reference Guide.
View Details of Storm Control PFC
You can view the status of storm control PFC and the statistical details by using the following Show commands.
Use the show storm-control pfc status stack-unit unit-number port—set portpipe-number command to view
the status of the storm control PFC on a specied stack unit. The following example shows the status on stack unit 0 with port set 0.
Dell#show storm-control pfc status stack-unit 0 port—set 0
------------------------------------------------------------------------------------------------
-----------
Interface Priority State Duration in discard state(in ms) Pkts
Dropped
------------------------------------------------------------------------------------------------
-----------
Te 0/0 3 Drop 15140 17365627
4 Drop 15040 17381908
5 Drop 15040 17381640
6 Drop 15040 17372119
Te 0/1 3 Normal 0 0
4 Normal 0 0
5 Normal 0 0
6 Normal 0 0
Te 0/2 3 Drop 14880 8682814
4 Drop 14880 8690956
5 Drop 14880 8690823
782
Storm Control