3.11. Configuring Flow Control

Overview

Function Introduction

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 to stop sending until the condition clears. When the local device detects any congestion at its end, it can notify the link partner or the remote device of the congestion by sending a pause frame. You can use the flowcontrol interface configuration command to set the interface’s ability to receive and send pause frames to on, off. The default state for ports is receive off and send off. In auto-negotiation link, local device’s flow control ability can be notified to link partner by link up/down.

image6 Flow control send/receive on ability only works on full duplex link.

Principle Description

N/A

Configuration

image

Fig. 3.18 Flow control

Configuring Flow Control Send

step 1 Enter the configure mode

Switch# configure terminal

step 2 Enter the interface configure mode and enable flowcontrol send

Switch(config)# interface eth-0-1
Switch(config-if)# flowcontrol send on

step 3 Exit the configure mode

Switch(config-if)# end

step 4 Validation

Use the following command to display the information of flow control:

Switch# show flowcontrol
Port Receive FlowControl Send FlowControl RxPause TxPause
admin oper admin oper
----- ---- --------------
eth-0-1 off off on on 0 0
eth-0-2 off off off off 0 0
eth-0-3 off off off off 0 0

Use the following command to display the information of flow control on specified interface:

Switch# show flowcontrol eth-0-1
Port Receive FlowControl Send FlowControl RxPause TxPause
admin oper admin oper
----- ---- ----- ----
eth-0-1 off off on on 0 0

Configuring Flow Control Receive

step 1 Enter the configure mode

Switch# configure terminal

step 2 Enter the interface configure mode and enable flowcontrol send

Switch(config)# interface eth-0-1
Switch1(config-if)# flowcontrol receive on

step 3 Exit the configure mode

Switch(config-if)# end

step 4 Validation

Use the following command to display the information of flow control:

Switch1# show flowcontrol
Port Receive FlowControl Send FlowControl RxPause TxPause
admin oper admin oper
----- ---- ----- ----
eth-0-1 on  on  off off 0 0
eth-0-2 off off off off 0 0
eth-0-3 off off off off 0 0

Use the following command to display the information of flow control on specified interface:

Switch1# show flowcontrol eth-0-1
Port Receive FlowControl Send FlowControl RxPause TxPause
admin oper admin oper
----- ---- ----- ----
eth-0-1 on on off off 0 0

Application cases

N/A