Cisco Systems 3560 Manual De Usuario

Flow control enables connected Ethernet ports to control traffic rates during congestion by allowing 
congested nodes to pause link operation at the other end. If one port experiences congestion and cannot 
receive any more traffic, it notifies the other port by sending a pause frame to stop sending until the 
condition clears. Upon receipt of a pause frame, the sending device stops sending any data packets, 
which prevents any loss of data packets during the congestion period.

Catalyst 3560 ports can receive, but not send, pause frames.

You use the flowcontrol interface configuration command to set the interface’s ability to receive pause 
frames to on, off, or desired. The default state is off.

When set to desired, an interface can operate with an attached device that is required to send 
flow-control packets or with an attached device that is not required to but can send flow-control packets. 

These rules apply to flow control settings on the device:

receive on (or desired): The port cannot send pause frames but can operate with an attached device 
that is required to or can send pause frames; the port can receive pause frames.

receive off: Flow control does not operate in either direction. In case of congestion, no indication 
is given to the link partner, and no pause frames are sent or received by either device.

For details on the command settings and the resulting flow control resolution on local and remote ports, 
see the flowcontrol interface configuration command in the command reference for this release.

Beginning in privileged EXEC mode, follow these steps to configure flow control on an interface:

To disable flow control, use the flowcontrol receive off interface configuration command.

This example shows how to turn on flow control on a port:

Switch# configure terminal

Switch(config)# interface gigabitethernet0/1

Switch(config-if)# flowcontrol receive on

Switch(config-if)# end

Enter global configuration mode.

interface interface-id

Specify the physical interface to be configured, and enter 
interface configuration mode.

flowcontrol {receive} {on | off | desired}

Configure the flow control mode for the port.

Return to privileged EXEC mode.

show interfaces interface-id

Verify the interface flow control settings.

(Optional) Save your entries in the configuration file.