the 10/100 and 10/100/1000 ethernet ports use standard rj-45 connectors and ethernet pinouts with　internal crossovers. these ports have the transmit (td) and receive (rd) signals internally crossed so　that a twisted-pair straight-through cable and adapter can be attached to the port. figure b-1 shows the　pinout for a 10/100 port.

   

    figure b-2 shows the pinout for a 10/100/1000 port.

   

    poe faults are caused when noncompliant cabling or powered devices are connected to a poe port. only standard-compliant cabling can be used to connect cisco pre-standard ip phones or wireless access points or ieee 802.3af-compliant devices to poe ports. a cable or device that causes a poe fault must be removed from the network.

    when connecting 10/100 and 10/100/1000 ports to 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 other 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-8 shows the four twisted-pair crossover cable schematics.

    you can use the mdix auto interface configuration command in the cli to enable the automatic medium-dependent interface crossover (auto-mdix) feature. when the auto-mdix 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, 10/100/1000, or 1000base-t sfp module port on the switch, regardless of the type of device on the other end of the connection.

    the auto-mdix feature is enabled by default on switches running cisco ios release 12.2(18)se or later. for releases between cisco ios release 12.1(14)ea1 and 12.2(18)se, the auto-mdix feature is disabled by default. for configuration information for this feature, see the switch software configuration guide or the switch command reference.

    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.

    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.

    this applies only to switches on which auto-mdix is disabled.