Duplex Settings

An Ethernet adapter and its link partner (such as a hub, switch, or another network adapter connected via a crossover cable) must operate at the same duplex settings.

• If the adapter and link partner support NWay media autonegotiation, both devices should automatically select optimal speed and duplex mode.

• If NWay autonegotiation is not supported or is not configured on either the adapter or its link partner, both devices must be explicitly set to run at the same duplex mode. A device usually defaults to half-duplex operation if it can't determine the link partner's duplex capabilities.

  • A hub or switch that supports full-duplex operation usually has a mechanism that sets duplex mode on a per-device or per-port basis. Setting speed, duplex mode, or both in this manner usually disables NWay autonegotiation for the device or port.

  • A network adapter supported by the dnet device driver must have its duplex mode set in the driver's .conf file. See the device driver man page for details.

    Operating speed can sometimes be set in the driver's .conf file, but NWay autonegotiation might be disabled when using this method.

    A device is usually able to detect the speed (but not the duplex mode) of its link partner, even without NWay autonegotiation.