Can a switch generate PFC Pause?

  • 14 September 2016
  • 12 replies
  • 298 views

Userlevel 1
I want my EXOS 670 switch to generate pause frames when it receives certain traffic or when its buffer is full. currently when i send the traffic from both ends it passes by without dropping. All packets sent are received. How to make one end stop sending one the other end is sending packets? in other words how to enable PFC on switch .

12 replies

Userlevel 4
Just an excerpt from the User Guide - You will find more infos there..

Userlevel 1
Thank you Andre but this only works when my end device is generating PFC pause. i want that the switch generates PFC pause in response to my flow. Is it possible?
Userlevel 6
Hi Danial,

You can find more information in the GTAC article below:

https://gtacknowledge.extremenetworks.com/articles/How_To/How-to-configure-Priority-Flow-Control
Userlevel 1
Yes thank you! what i am doing here is attach a test center to exos on ports say 1 and 2. now i want is if port 1 and 2 sends frames simultaneously port 1 should be paused for a while. how can i do it inside the switch because both ports can have priority 3 traffic how should i pause priority 3 traffic of say port 2.
Userlevel 6
Hi Danial, I haven't tried that yet, but I guess you can accomplish that with the command below:

enable flow-control tx-pause priority 3 ports 2

The default dot1p priority values are:

802.1p Priority Value QOS Profile
1 QP1
2 QP1
3 QP1
4 QP1
5 QP1
6 QP1
7 QP8
Userlevel 1
No i tried this but its not working. I have the two ports in a single vlan and i applied the same command but both the ends can still receive the frames..
Userlevel 6
Hi Danial, did you try the same command for rx-pause as well?

Do you see any counter incrementing to the commands below?

show port 1,2 flow-control tx-pauses
show port 1,2 flow-control rx-pauses
Userlevel 1
there is no command for counters
X670V-48x.1 # show port 1
Execute the command
anomaly anomaly statistics
buffer Show packet buffering information
collisions Displays collision statistics
configuration Display the port configuration
congestion Display congestion statistics
debounce Display amount of time to delay link down detection
description Displays description associated with the port
information Displays port information
ip-fix Displays IP Flow Information Export (IPFIX) statistics
no-refresh Page by page display without auto-refresh
packet histogram of packet statistics
qosmonitor QOS
rate-limit Displays rate-limit discard statistics
rxerrors receive error statistics
sharing Load sharing
statistics Port statistics
transceiver DDMI info
txerrors Displays transmit error statistics
utilization Port utilization information
vlan VLAN Statistics
wred Display WRED statistics

Userlevel 6
there is no command for counters
X670V-48x.1 # show port 1
Execute the command
anomaly anomaly statistics
buffer Show packet buffering information
collisions Displays collision statistics
configuration Display the port configuration
congestion Display congestion statistics
debounce Display amount of time to delay link down detection
description Displays description associated with the port
information Displays port information
ip-fix Displays IP Flow Information Export (IPFIX) statistics
no-refresh Page by page display without auto-refresh
packet histogram of packet statistics
qosmonitor QOS
rate-limit Displays rate-limit discard statistics
rxerrors receive error statistics
sharing Load sharing
statistics Port statistics
transceiver DDMI info
txerrors Displays transmit error statistics
utilization Port utilization information
vlan VLAN Statistics
wred Display WRED statistics



It seems that you are using an older EXOS code.

This command was first available in EXOS 15.6.2.
Userlevel 1
there is no command for counters
X670V-48x.1 # show port 1
Execute the command
anomaly anomaly statistics
buffer Show packet buffering information
collisions Displays collision statistics
configuration Display the port configuration
congestion Display congestion statistics
debounce Display amount of time to delay link down detection
description Displays description associated with the port
information Displays port information
ip-fix Displays IP Flow Information Export (IPFIX) statistics
no-refresh Page by page display without auto-refresh
packet histogram of packet statistics
qosmonitor QOS
rate-limit Displays rate-limit discard statistics
rxerrors receive error statistics
sharing Load sharing
statistics Port statistics
transceiver DDMI info
txerrors Displays transmit error statistics
utilization Port utilization information
vlan VLAN Statistics
wred Display WRED statistics



yes, but how to check the buffers in this code?
Userlevel 1
there is no command for counters
X670V-48x.1 # show port 1
Execute the command
anomaly anomaly statistics
buffer Show packet buffering information
collisions Displays collision statistics
configuration Display the port configuration
congestion Display congestion statistics
debounce Display amount of time to delay link down detection
description Displays description associated with the port
information Displays port information
ip-fix Displays IP Flow Information Export (IPFIX) statistics
no-refresh Page by page display without auto-refresh
packet histogram of packet statistics
qosmonitor QOS
rate-limit Displays rate-limit discard statistics
rxerrors receive error statistics
sharing Load sharing
statistics Port statistics
transceiver DDMI info
txerrors Displays transmit error statistics
utilization Port utilization information
vlan VLAN Statistics
wred Display WRED statistics



Can I give a timer value for PFC inside the switch?
Userlevel 6
there is no command for counters
X670V-48x.1 # show port 1
Execute the command
anomaly anomaly statistics
buffer Show packet buffering information
collisions Displays collision statistics
configuration Display the port configuration
congestion Display congestion statistics
debounce Display amount of time to delay link down detection
description Displays description associated with the port
information Displays port information
ip-fix Displays IP Flow Information Export (IPFIX) statistics
no-refresh Page by page display without auto-refresh
packet histogram of packet statistics
qosmonitor QOS
rate-limit Displays rate-limit discard statistics
rxerrors receive error statistics
sharing Load sharing
statistics Port statistics
transceiver DDMI info
txerrors Displays transmit error statistics
utilization Port utilization information
vlan VLAN Statistics
wred Display WRED statistics



Hi Danial, I don't see an option to configure a time value for PFC.

To have the PFC being generated by the switch, the frames with priority 3 (in your case) should be congested.

Could you please check if one of the following commands shows any increment and share the results:

show port congestion
show port qosmonitor
show port qosmonitor congestion

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