Mastering mii-tool: Configure and Diagnose Network Interface Negotiation
This guide explains how to use the mii-tool command on Linux to view, configure, and troubleshoot network interface negotiation settings, covering syntax, option meanings, and practical examples for setting duplex modes and restoring auto‑negotiation.
mii-tool: Network Device Negotiation Tool
Function Description
The mii-tool command can be used to view and configure the negotiation mode of network devices.
Sometimes a NIC needs its negotiation mode set manually—for example, configuring a 10/100/1000 Mb/s NIC to half‑duplex, full‑duplex, or auto‑negotiation. Most devices use auto‑negotiation by default, but when issues such as high packet loss occur, manual configuration becomes necessary.
Command Syntax
mii-tool [options] [device_interface]Option Meanings
-v : display NIC information
-F : change the NIC negotiation mode
-r : restore the NIC to auto‑negotiation mode
-R : reset MII to the up state
-w : show changes in NIC link status
-l : write events to the system log
-A : specify a particular network interface
-V : display version information
Reference Examples
(1) View the working mode of NIC ens33
# mii-tool ens33
ens33: negotiated 1000baseT-FD flow-control, link ok(2) Set the NIC to operate at 100 Mb/s half‑duplex # mii-tool -F 100baseTx-HD ens33 (3) View detailed information of the NIC
# mii-tool -v ens33
ens33: 1000 Mbit, half duplex, link ok
product info: Yukon 88E1011 rev 3
basic mode: 100 Mbit, half duplex
basic status: link ok
capabilities: 1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
advertising: 1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
link partner: 1000baseT-HD 1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD(4) Restore the NIC to auto‑negotiation mode
# mii-tool -r ens33
restarting autonegotiation...(5) Verify the NIC is now in auto‑negotiation mode
# mii-tool -v ens33
ens33: negotiated 1000baseT-FD flow-control, link ok
product info: Yukon 88E1011 rev 3
basic mode: autonegotiation enabled
basic status: autonegotiation complete, link ok
capabilities: 1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
advertising: 1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
link partner: 1000baseT-HD 1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HDSigned-in readers can open the original source through BestHub's protected redirect.
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