mii-tool(8)
View or manipulate media-independent interface status and configuration for Ethernet devices.
Synopsis
mii-tool [OPTION]... [INTERFACE]...Description
mii-tool queries and configures the media-independent interface (MII) status of Ethernet devices. It reports link status, speed, and duplex mode, and can force specific speed/duplex settings on network interfaces.
This tool is useful for diagnosing network hardware issues, checking auto-negotiation status, and forcing half or full duplex when auto-negotiation fails. Modern systems often use ethtool instead, but mii-tool remains available on many distributions.
Common options
| Flag | What it does |
|---|---|
-A, --advertise=MEDIA | Advertise only the specified media types during auto-negotiation (e.g., 100baseTx-FD) |
-F, --force=MEDIA | Force the specified speed and duplex (e.g., 100baseTx-FD, 10baseT-HD); disables auto-negotiation |
-r, --restart | Restart auto-negotiation on the specified interface |
-R, --reset | Reset the MII interface |
-l, --log | Monitor link status and log changes to syslog |
-w, --watch | Continuously monitor link status and display changes in real-time |
-v, --verbose | Display more detailed output including raw MII register values |
-p, --phy | Specify the PHY address to query (advanced use) |
Examples
Display the current media type, speed, duplex mode, and status of eth0
mii-tool eth0Show detailed MII status including raw register values for eth0
mii-tool -v eth0Force eth0 to 100 Mbps, full duplex (disables auto-negotiation)
mii-tool -F 100baseTx-FD eth0Force eth0 to 10 Mbps, half duplex for backward compatibility with older equipment
mii-tool -F 10baseT-HD eth0Restart auto-negotiation on eth0 to renegotiate link speed and duplex
mii-tool -r eth0Continuously monitor eth0 and display any changes to link status in real-time
mii-tool -w eth0Display status of multiple interfaces eth0 and eth1
mii-tool eth0 eth1