Setting The Interface Speed And Duplex Parameters - Cisco 3845 - Security Bundle Router Software Manual

Chapter 9 Configuring Interfaces
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Caution Changing the interface speed and duplex mode configuration might shut down and re-enable the
interface during the reconfiguration.

Setting the Interface Speed and Duplex Parameters

Beginning in privileged EXEC mode, follow these steps to set the speed and duplex mode for a physical
interface.
Command
Step 1
configure terminal
Step 2
interface interface-id
OL-23400-01
The exception is when a 1000BASE-T SFP module is in the SFP module slot, you can configure
speed as 10, 100, or 1000 Mb/s, or auto, but not as nonegotiate.
On a 100BASE-FX SFP module, you cannot configure the speed as nonegotiate.
You cannot configure duplex mode on 10 GigabitEthernet ports. The duplex command is not
available.
You cannot configure duplex mode on SFP module ports; they operate in full-duplex mode except
in these situations:
When a Cisco1000BASE-T SFP module is in the SFP module slot, you can configure duplex
–
mode to auto or full. Half-duplex mode is supported with the auto setting.
– When a Cisco100BASE-FX SFP module is in the SFP module slot, you can configure duplex
mode to half or full. Although the auto keyword is available, it puts the interface in half-duplex
mode (the default for this SFP module) because the 100BASE-FX SFP module does not support
autonegotiation.
If both ends of the line support autonegotiation, we highly recommend the default setting of auto
negotiation.
If one interface supports autonegotiation and the other end does not, configure duplex and speed on
both interfaces; do not use the auto setting on the supported side.
When STP is enabled and a port is reconfigured, the switch can take up to 30 seconds to check for
loops. The port LED is amber while STP reconfigures.
Purpose
Enter global configuration mode.
Specify the physical interface to be configured, and enter interface
configuration mode.
Cisco ME 3800X and 3600X Switch Software Configuration Guide
Configuring Ethernet Interfaces
9-15