Ethernet flow control can be used to control the pace of data packet flows across interfaces. When the volume of packets ingressing into an interface exceeds that interface’s ability to process/buffer them, those packets will normally be dropped. Flow control provides for the transmission of pause frames which tell the sender to pause transmission for a specified period when the receiver is overwhelmed. Data transmission rates can be slower as a result, but with the payoff of fewer dropped packets.Flow control is disabled by default, but is available on all AW+ devices, providing the following criteria are met:
- It must be enabled on both ends of a connection
- Full-duplex mode must be enabled
- It is enabled at the interface level
- It can be enabled on physical ports, not virtual layer 3 interfaces.
- It can be enabled for transmission only, receiving only, or both directions.
To enable flow control…
awplus#conf t
Enter configuration commands, one per line. End with CNTL/Z.
awplus(config)#int port1.0.1
awplus(config-if)#flowcontrol [both | receive | send]
To disable…
awplus#conf t
Enter configuration commands, one per line. End with CNTL/Z.
awplus(config)#int port1.0.1
awplus(config-if)#no flowcontrol
To verify flow control status…
awplus#show flowcontrol [interface.x.x (optional)]
Port Send FlowControl Receive FlowControl RxPause TxPause
admin oper admin oper
----- ----- ----------- ------- ----------- ------- -------
port1.0.1 on on on on 0 7566
To clear flow control counters…
awplus#clear port counter [IFNAME (optional)]