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Configuring Interfaces
Configuring Ethernet Interfaces
To disable 802.3x flow control, use the flowcontrol receive off interface configuration command.
This example shows how to enable 802.3x flow control on a port:
Switch# configure terminal
Switch(config)# interface GigabitEthernet1/17
Switch(config-if)# flowcontrol receive on
Switch(config-if)# end
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 Mbps 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 4 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:
5. end Return to privileged EXEC mode.
6. show interfaces interface-id Verify the interface 802.3x flow control settings.
7. copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
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
1. configure terminal Enter global configuration mode
2. interface interface-id Specify the physical interface to be configured, and enter interface
configuration mode.
3. no shutdown Enable the port, if necessary. By default, UNIs and ENIs are disabled, and
NNIs are enabled.
4. speed auto Configure the interface to autonegotiate speed with the connected device.
5. duplex auto Configure the interface to autonegotiate duplex mode with the connected
device.
6. mdix auto Enable auto-MDIX on the interface.
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