Configuring Ieee 802.3X Flow Control - Cisco Catalyst 2928 Software Configuration Manual

Chapter 12 Configuring Interface Characteristics
For interfaces gi0/1 to gi0/16, speed and duplex settings do not apply, as they are only internal
Note
server-facing interfaces. For interfaces 17 to 20, speed and duplex do not apply when they are operating
in SFP module mode. For interfaces gi0/23 and gi0/24, speed and duplex do not apply when configured
for media-type internal. For more information, see the

Configuring IEEE 802.3x Flow Control

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 2928 ports can receive, but not send, pause frames.
Note
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:
•
•
For details on the command settings and the resulting flow control resolution on local and remote ports,
Note
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:
Command
Step 1
configure terminal
Step 2 interface interface-id
Step 3 flowcontrol {receive} {on | off | desired}
Step 4 end
Step 5 show interfaces interface-id
Step 6
copy running-config startup-config
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
OL-23389-01
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.
"Access Ports" section on page
Purpose
Enter global configuration mode
Specify the physical interface to be configured, and enter
interface configuration mode.
Configure the flow control mode for the port.
Return to privileged EXEC mode.
Verify the interface flow control settings.
(Optional) Save your entries in the configuration file.
Catalyst 2928 Switch Software Configuration Guide
Configuring Ethernet Interfaces
12-2.
12-19