TOOL-MII (media-independent interface status manipulation tool) is a tool which can verify or set the status of unity of the Middle Independent Interface (MII) of the network interface (NIC).
Most fast ethernet adapters use the MII for autonegociar speed link (link) and adjust your duplex. These devices use a protocol for communicating autonegociacion technologies which means bear, and so in this way to use technology more quickly supported each other.

Some passive devices such as hubs speed simple (single-speed hubs), have no ability to autonegociacion. To support these devices MII protocol allows the connection with only detect the heartbeat of the link to 10baseT or 100baseT.

It is possible to force the mode of operation of the protocol with the MII or option-F-force. The report by default displays the speed and the status of the link for each interface. If a NIC interface or was not specified on the command line, mii-tool monitor all interfaces available from eth0 up eth7.

Below are some examples of how to view, change or adjust the speed of our network via the ethernet interface:

  • View settings accepted by our interfaces with the hub / router / switch ...: 
    •   deathbian: ~ # mii-tool 
  eth0: FD negotiated 100BaseTX-flow-control, link ok 
  deathbian: ~ #


  • Specify the link to 10 Mbps, full duplex: 
    •   deathbian: ~ # mii-tool - force = 10baseT-FD eth0


  • Specify the link to 10 mbps, half duplex: 
    •   deathbian: ~ # mii-tool - force = 10baseT-HD eth0


  • Specify the link to 100 Mbps, full duplex: 
    •   deathbian: ~ # mii-tool - force = 100BaseTX-FD eth0


  • Specify the link to 100 mbps, half duplex: 
    •   deathbian: ~ # mii-tool - force = 100BaseTX-HD eth0


I have written this howto since the mii-tool use in servers Red Hat 6.x, 7.x, 8, 9. For software, or more modern versions of Linux (CentOS 5, Debian 3.4, SUSE 10, etc.) there is the tool ethtool to change the settings of the ethernet card.

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