Users Guide

PFC Storm
When packets flood a network, the result is excessive traffic which affects the performance of the network.
When Priority Flow Control (PFC) is enabled on a port, the traffic flows according to the priority of the data.
PFC storm is the inconsistencies found in the traffic that flows through a PFC enabled port. You can detect
this by polling the lossless queues on each port. This polling is done at periodic intervals. If the queue has
traffic with the corresponding egress counter not getting incremented, then the condition is detected as PFC
storm. During such conditions, the traffic corresponding to the port or priority can be dropped for a specific
period of time to overcome the degrade in the network performance.
Once you detect PFC storm on a port or priority, you can discard all packets on that port/priority and enable
drop of the queue, so that traffic corresponding to other priorities is not affected. You can restore the
dropped queue to normal state after a period of time.
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 specified 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
Storm Control 966