User manual

I NTERFACE C OMMANDS
4-173
Command Usage
• Flow control can eliminate frame loss by “blocking” traffic from end
stations or segments connected directly to the switch when its buffers
fill. When enabled, back pressure is used for half-duplex operation and
IEEE 802.3x for full-duplex operation.
• To force flow control on or off (with the flowcontrol or no
flowcontrol command), use the no negotiation command to disable
auto-negotiation on the selected interface.
• When using the negotiation command to enable auto-negotiation,
the optimal settings will be determined by the capabilities command.
To enable flow control under auto-negotiation, “flowcontrol” must
be included in the capabilities list for any port
• Avoid using flow control on a port connected to a hub unless it is
actually required to solve a problem. Otherwise back pressure
jamming signals may degrade overall performance for the segment
attached to the hub.
Example
The following example enables flow control on port 5.
Related Commands
negotiation (4 -170)
capabilities (flowcontrol, symmetric) (4-171)
Console(config)#interface ethernet 1/5
Console(config-if)#flowcontrol
Console(config-if)#no negotiation
Console(config-if)#