Configuring Auto-Negotiation
For Cisco switches, auto-negotiation is enabled by default. You can configure the
speed and duplex mode manually with the speed
and
duplex
interface commands in IOS.
You cannot set the duplex mode without first setting the speed. The switch will complain if you attempt to do so:
2950(config-if)#duplex half
Duplex can not be set until speed is set to non-auto value
To set the speed of the interface, use the speed
command. If the interface has previously been configured, you can return it to
auto-negotiation with the auto
keyword:
2950(config-if)#speed ?
10 Force 10 Mbps operation
100 Force 100 Mbps operation
auto Enable AUTO speed configuration
Once you've set the speed, you can set the duplex mode to auto
, full
, or half
:
2950(config-if)#duplex ?
auto Enable AUTO duplex configuration
full Force full duplex operation
half Force half-duplex operation
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