9-18
Cisco ME 3800X and 3600X Switch Software Configuration Guide
OL-23400-01
Chapter 9 Configuring Interfaces
Configuring Ethernet Interfaces
Configuring Auto-MDIX on an Interface
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 switches 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 switches 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.
Auto-MDIX is enabled by default. When you enable auto-MDIX, you must also set the speed and duplex
on the interface to auto so that the feature operates correctly. Auto-MDIX is supported on all 10/100 and
10/100/1000 Mb/s interfaces and on Cisco 10/100/1000 BASE-T/TX SFP module interfaces. It is not
supported on 1000 BASE-SX or -LX SFP module interfaces.
Table 9-3
shows the link states that result from auto-MDIX settings and correct and incorrect cabling.
Beginning in privileged EXEC mode, follow these steps to configure auto-MDIX on an interface:
To disable auto-MDIX, use the no mdix auto interface configuration command.
This example shows how to enable auto-MDIX on a port:
Switch#
configure terminal
Switch(config)#
interface gigabitethernet0/1
Switch(config-if)#
speed auto
Switch(config-if)#
duplex auto
Switch(config-if)#
mdix auto
Table 9-3
Link Conditions and Auto-MDIX Settings
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
Purpose
Step 1
configure terminal
Enter global configuration mode
Step 2
interface interface-id
Specify the physical interface to be configured, and enter interface
configuration mode.
Step 3
speed auto
Configure the interface to autonegotiate speed with the connected device.
Step 4
duplex auto
Configure the interface to autonegotiate duplex mode with the connected
device.
Step 5
mdix auto
Enable auto-MDIX on the interface.
Step 6
end
Return to privileged EXEC mode.
Step 7
show controllers ethernet-controller
interface-id phy
Verify the operational state of the auto-MDIX feature on the interface.
Command is there, but no mdix in output.
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.