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Automatic medium-dependent interface crossover (auto-MDIX) is enabled by default.
Auto-MDIX is supported on all 10/100/1000-Mb/s and on 10/100/1000BASE-TX small form-factor pluggable (SFP)-module interfaces. It is not supported on 1000BASE-SX or -LX SFP module interfaces.
The device might not support a pre-standard powered device—such as Cisco IP phones and access points that do not fully support IEEE 802.3af—if that powered device is connected to the device through a crossover cable. This is regardless of whether auto-MIDX is enabled on the switch port.
When automatic medium-dependent interface crossover (auto-MDIX) is enabled on an interface, the interface automatically detects the required cable connection type (straight through or crossover) and configures the connection appropriately. When connecting devices without the auto-MDIX feature, you must use straight-through cables to connect to devices such as servers, workstations, or routers and crossover cables to connect to other devices or repeaters. With auto-MDIX enabled, you can use either type of cable to connect to other devices, and the interface automatically corrects for any incorrect cabling. For more information about cabling requirements, see the hardware installation guide.
This table shows the link states that result from auto-MDIX settings and correct and incorrect cabling.
|
Local Side Auto-MDIX |
Remote Side Auto-MDIX |
With Correct Cabling |
With Incorrect Cabling |
|---|---|---|---|
|
On |
On |
Link up |
Link up |
|
On |
Off |
Link up |
Link up |
|
Off |
On |
Link up |
Link up |
|
Off |
Off |
Link up |
Link down |
| Command or Action | Purpose | |
|---|---|---|
| Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
| Step 2 |
configure terminal Example: |
Enters global configuration mode |
| Step 3 |
interface interface-id Example: |
Specifies the physical interface to be configured, and enter interface configuration mode. |
| Step 4 |
speed auto Example: |
Configures the interface to autonegotiate speed with the connected device. |
| Step 5 |
duplex auto Example: |
Configures the interface to autonegotiate duplex mode with the connected device. |
| Step 6 |
end Example: |
Returns to privileged EXEC mode. |
| Step 7 |
copy running-config startup-config Example: |
(Optional) Saves your entries in the configuration file. |
This example shows how to enable auto-MDIX on a port:
Switch# configure terminal
Switch(config)# interface gigabitethernet 1/0/1
Switch(config-if)# speed auto
Switch(config-if)# duplex auto
Switch(config-if)# mdix auto
Switch(config-if)# end
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