C
OMMAND
L
INE
I
NTERFACE
3-98
Command Mode
Interface Configuration (Ethernet, Port Channel)
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.
• 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.
• To force flow control on or off (with the flowcontrol or no
flowcontrol comm and), use the no negotiation command to
disable auto-negotiation on the selected interface.
• 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.
• Due to a hardware limitation, flow control only works on those
ports located in the same chip (ports 1-12 and ports 13-24).
Cross-chip flow control does not work.
Example
The following example enables flow control on port 5.
Related Commands
capabilities (3-96) (flowcontrol (3-97), symmetric)
Console(config)#interface ethernet 1/5
Console(config-if)#flowcontrol
Console(config-if)#no negotiation
Console(config-if)#
b_mgmt.book Page 98 Tuesday, July 8, 2003 5:24 PM