Interface Commands
27-6
27
Command Usage
• 1000BASE-T and 10GBASE-T do not support forced mode. Auto-negotiation
should always be used to establish a connection over any 1000BASE-T or
10GBASE-T port or trunk.
• 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 802.3-2005
(formally 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 (27-4)
capabilities (flowcontrol, symmetric) (27-4)
media-type
This command forces the port type selected for combination ports 21-24/45-48. Use
the no form to restore the default mode.
Syntax
media-type mode
no media-type
• mode
- copper-forced - Always uses the built-in RJ-45 port.
- sfp-forced - Always uses the SFP port (even if module not installed).
- sfp-preferred-auto - Uses SFP port if both combination types are
functioning and the SFP port has a valid link.
Default Setting
sfp-preferred-auto
Console(config)#interface ethernet 1/5
Console(config-if)#flowcontrol
Console(config-if)#no negotiation
Console(config-if)#
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