you can set the 10/100 on the switch to operate in any combination of half duplex, full duplex, 10 mbps or 100 mbps. you can set the 10/100/1000 ports to operate in 10 mbps, 100 mbps, or 1000 mbps in full duplex. you can also set these ports for speed and duplex autonegotiation in compliance with ieee 802.3ab. (the default setting is autonegotiate.) when set for autonegotiation, the port senses the speed and duplex settings of the attached device and advertises its own capabilities. if the connected device also supports autonegotiation, the switch port negotiates the best connection (that is, the fastest line speed that both devices support and full-duplex transmission if the attached device supports it) and configures itself accordingly. in all cases, the attached device must be within 328 feet (100 meters).

    100base-tx and 1000base-t traffic requires category 5 cable. 10base-t traffic can use category 3 or category 4 cables.

    when connecting the switch to workstations, servers, routers, and cisco ip phones, be sure that the cable is a straight-through cable. when connecting the switch to switches or hubs, use a crossover cable. when using a straight-through or crossover cable for 1000base-t connections, be sure to use a twisted four-pair, category 5 cable for proper operation. pinouts for the cables are described in appendix b, “connector and cable specifications.”

    on switches running cisco ios release 12.1(14)ea1 or later, you can use the mdix auto command in the cli to enable the automatic crossover feature. when the automatic crossover feature is enabled, the switch detects the required cable type for copper ethernet connections and configures the interfaces accordingly.

    therefore, you can use either a crossover or a straight-through cable for connections to a copper 10/100 or 10/100/1000 port on the switch, regardless the type of device on the other end of the connection.

    the automatic crossover feature is disabled by default. for configuration information for this feature, refer to the switch software configuration guide or the switch command reference.