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.
connecting to 10base-t- and 100base-tx-compatible devices
when connecting the ports to 10base-t- and 100base-tx-compatible devices, such as servers, workstations, and routers, you can use a two or four twisted-pair, straight-through cable wired for 10base-t and 100base-tx. figure b-5 shows the two twisted-pair, straight-through cable schematics. figure b-7 shows the four twisted-pair, straight-through cable schematics.
when connecting the ports to 10base-t- and 100base-tx-compatible devices, such as switches or repeaters, you can use a two or four twisted-pair, crossover cable. figure b-6 shows the two twisted-pair, crossover cable schematics.
figure b-10 shows the four twisted-pair, crossover cable schematics.
you can use category 3, 4, or 5 cabling when connecting to 10base-t-compatible devices. you must use category 5 cabling when connecting to 100base-tx-compatible devices.
connecting to 1000base-t devices
when connecting the ports to 1000base-t devices, such as servers, workstations, and routers, you must use a four twisted-pair, category 5, straight-through cable wired for 10base-t, 100base-tx, and 1000base-t.
figure b-9 shows the straight-through cable schematics.
when connecting the ports to other devices, such as switches or repeaters, you must use a four twisted-pair, category 5, crossover cable. figure b-10 shows the crossover cable schematics.
be sure to use a four twisted-pair, category 5 cable when connecting to a 1000base-t-compatible device.
use a straight-through cable to connect two ports only when one port is designated with an x. use a crossover cable to connect two ports when both ports are designated with an x or when both ports do not have an x.
