MII-TOOL(8)

🎀 NAME 🎀

okay so bestie, this is mii-tool 🦋 and it's giving "check your network interface's MII status" energy. It's all about viewing and manipulating the media-independent interface status ✨

💅 SYNOPSIS 💅

mii-tool [-v, --verbose] [-V, --version] [-R, --reset] [-r, --restart]
[-w, --watch] [-l, --log] [-A, --advertise=media,...]  [-F,
--force=media] [-p, --phy=addr] interface ...

💖 DESCRIPTION 💖

okay so this utility checks or sets the status of a network interface's Media Independent Interface (MII) unit 🔥 Most fast ethernet adapters use an MII to autonegotiate link speed and duplex setting, so it's lowkey the thing doing the heavy lifting 🌸

Most intelligent network devices use an autonegotiation protocol to say what media technologies they support, and then pick the fastest one everyone can agree on 🫶 The -A or --advertise options let you tell the MII to only advertise a subset of its capabilities. Some passive devices, like single-speed hubs, can't autonegotiate at all 💀 For those, the MII protocol can still establish a link by just detecting a 10baseT or 100baseT link beat. That's where -F or --force comes in, forcing the MII to run in one mode instead of negotiating ✨ Just know that -A and -F are mutually exclusive, so you can't use both at once, no cap 🙅‍♀️

The default short output reports the negotiated link speed and link status for each interface 🧚

🌈 OPTIONS 🌈

• -v, --verbose — shows more detailed MII status info 🔍 Use it twice and you also get the raw MII register contents 💜

⚠️ Alert: if you go three times, it'll force a read of all MII registers, including the non-standard ones 😭 There's no guarantee you'll get a valid answer from the PHY, and PHY communication can even hang. With the e1000e driver, reading register 0x07 will fail 💀

• -V, --version — shows the program version info 🎀
• -R, --reset — resets the MII back to its default configuration 🔄
• -r, --restart — restarts autonegotiation 🚀
• -w, --watch — watches the interface(s) and reports link status changes 👀 The MII interfaces get polled every one second ⏱️
• -l, --log — used together with -w, this records link status changes in the system log instead of printing them to standard output 📜
• -F media, --force=media — disables autonegotiation and forces the MII into either 100baseTx-FD, 100baseTx-HD, 10baseT-FD, or 10baseT-HD operation 💅
• -A media,..., --advertise=media,... — enables and restarts autonegotiation, but only advertises the media technologies you pick 🫧 Separate multiple technologies with commas. The valid media are 100baseT4, 100baseTx-FD, 100baseTx-HD, 10baseT-FD, and 10baseT-HD 🍓
• -p addr, --phy=addr — overrides the MII address the kernel gave you with the value addr 🧚‍♀️

🙈 DIAGNOSTICS 🙈

when stuff goes wrong, these are the errors you'll see, iykyk 😭

• SIOCGMIIPHY on 'eth?' failed: Invalid argument — if the interface isn't running (up), the kernel will refuse to report its link state 🙅‍♀️
• SIOCGMIIPHY on 'eth?' failed: Operation not permitted — most kernels restrict access to root, so try again as root 👑
• SIOCGMIIPHY on 'eth?' failed: No such device — this one pops up when the kernel doesn't know about the named device 🫠
• SIOCGMIIPHY on 'eth?' failed: Operation not supported — the interface in question doesn't support MII queries. Most likely it doesn't have MII transceivers at all, bestie 💔

🦋 AUTHORS 🦋

these are the legends who made it happen 🫶

• David Hinds - dhinds@pcmcia.sourceforge.org
• Donald Becker - becker@scyld.com
• Bernd Eckenfels - net-tools@lina.inka.de

✨ SEE ALSO ✨

if you want to go deeper, check out the homepage of the net-tools project at http://net-tools.sourceforge.net 🌐

💖 and that's the tea, bestie! mii-tool from the net-tools project, dated 2013-02-15 💅✨