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flowcontrol of cisco 2960s

Hello all,

I met a strange problem after enabling flowcontrol in 2960s.

my enviroment,

- 2 cisco 2960s 24ts-l have been created a stack

- IOS is 12.2(58)se2

- all ports have been enabled flowcontrol receive dersied

via show flowcontrol, I can see each Gigabyte Port have been enabled "flowcontrol receive desired" but, when I do the following tests

- connect equallogic ps4000xv to the port 21, I found the status of port is "input flow-control is off"

- connect one server with Broadcom Gigabyte Network adapter, which has been enable TX ON RX ON, or Auto, the status of the port is still  "input flow-control is off"    

I guess, the port status should be ""input flow-control is on". Test them with another port, I got the same result. why?

I attached the config file and the port status file.

Any help will be appreciated.



Accepted Solutions

Glad you sorted it and thanks for feeding back to the forum.

Now that it's working, you can switch it off as generally recommended

View solution in original post


Are the servers and switchports all set to auto-negotiate speed/duplex?




The flowcontrol receive desired command enables the switch to utilise any pause frames it receives from your servers.

The 2960 cannot send pause frames, hence your servers report 'input flow-control is off'.

If your servers are enabled to send pause frames to the 2960, then flowcontrol should work in that direction only.


Thank you, Shillings

Yes, 2960s can't send pause frames, but can receive.

my question is why the port status of  the switch is "'input flow-control is off'", actually, this port is connected to the server, which network adapter has been enabled flowcontrol.


Appologies, I misinterpreted your original post.

I couldn't find any other commands that might help you on the Cisco side. You've already tried two different servers, so not sure what else to suggest other than another switch, but I imagine that's not going to be very practical.


Hi Shillings,

I just tried to connect the server to a Dell PowerConnect 62xx Switch with flowcontrol enabled, and I found the port status about flowcontrol of Dell swtich will change if I change disable/enable the flowcontrol from the server side.

Besides, I also tried to connect the server to a Cisco 3560g switch(flowcontrol receive desired) with the same IOS version, the same result occureed as 2960s switch's

It really drive me crazy.


I've searched the net and can't find anything useful relating to this. A few instances of people recommending you don't apply any flow control and leave it to TCP to handle, but I think it's more of an issue if the switch is doing outbound flow control, which you are not.

It would be good to confirm one of the servers is definitely applying outbound flow control. A registry setting or command line perhaps...


yes I've tried.

Configured the server definitely with "TX" ONLY, but got the same result.

Details of my switches.

- 2 cisco 2960s created a stack,

- I created 2 VLAN, VLAN3, and VLAN4

- All ports in VLAN3 and VLAN4 have enabled "flowcontrol recive deisred"

- Test port 21 is in VLAN 4 (actaully, I've tested other ports in VLAN 3, the same result.)


Have you tried flowcontrol receive on to see if that makes any difference?

Driver software on the servers perhaps? This thread was posted by another member who's servers were set to send flowcontrol, but it wasn't working. Unfortunately, there was never any resolution.


Yes, I tried flowcontrol receive on, but got the same result.

Today, I tired the flowcontrol control test on 2 cisco 3560g swithes, 3 cisco 2960s switches, with the same server and laptop, (this server and laptop actaully have been enalbed flow control, and tested successfully in the Dell powerconnect switch), butll all swithes dsiplayed the same status of the ports about flowcontrol.

All those switches are running the same IOS version - 12.2 (58) (SE2)

Did I make some mistakes in the IOS configuraiton?


Today, I upgarded the IOS to 15.0(2)SE,  the flowcontrol works.

I think it is a bug in IOS 12.2(58)SE2


Glad you sorted it and thanks for feeding back to the forum.

Now that it's working, you can switch it off as generally recommended

View solution in original post

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