Use this command if the equipment on the other end is capable of full-duplex mode.
This command specifies full-duplex mode on full-duplex single-mode and multimode port adapters available on the following networking devices:
Cisco 7200 series routers
Second-generation Versatile Interface Processors (VIP2s) in Cisco 7500 series routers
Serial interface ports that uses bisynchronous tunneling
Refer to the CiscoProductCatalog for hardware compatibility information and for specific model numbers of port adapters.
To enable half-duplex mode, use the nofull-duplex or half-duplex command.
For the Cisco AS5300, the duplexfull| halfauto} command replaces the full-duplex and half-duplex commands. You will get the following error messages if you try to use the full-duplex and half-duplex commands on a Cisco AS5300: Router(config)# interfacefastethernet0 Router(config-if)# full-duplex Please use duplex command to configure duplex mode Router(config-if)# Router(config-if)# half-duplex Please use duplex command to configure duplex mode
Support for This Command
Use the question mark (?) command to find out which port adapters support this command. If the interface does not support full-duplex, an informational message displayed, and no changes are made to the interface. To determine if the interface supports full-duplex, use the showinterfacescommand. For example, the following message is displayed if the interface does not support full-duplex:
% interface does not support full-duplex.
Use on FDDI
Full-duplex on the FDDI full-duplex port adapters allows an FDDI ring with exactly two stations to transform the ring into a full-duplex, point-to-point topology. For the interface to operate in full-duplex mode, there must be only two stations on the ring, the two stations must be capable of operating in full-duplex mode, and both stations must complete a full-duplex autoconfiguration protocol. There is no FDDI token in full-duplex mode. Refer to the CiscoProductCatalog for specific model numbers of port adapters.
Full-duplex autoconfiguration protocol allows an FDDI station to dynamically and automatically operate in either half-duplex (or ring) or full-duplex mode, and ensures that the stations fall back to ring mode when a configuration change occurs, such as a third station joining the ring.
After booting the router, the FDDI stations begin operation in half-duplex mode. While the station performs the full-duplex autoconfiguration protocol, the station continues to provide data-link services to its users. Under normal conditions, the transition between half-duplex mode and full-duplex mode is transparent to the data-link users. The data-link services provided by full-duplex mode are functionally the same as the services provided by half-duplex mode.
If you change the full-duplex configuration (for example, from disabled to enabled) on supported interfaces, the interface resets.
Cisco 10000 Series Router
The Fast Ethernet line card responds only to 802.3x pause frames from another device when it autonegotiates the duplex mode (the default). The line card does not support 802.3x flow control when you manually set half-duplex or full-duplex mode.