MII-DIAG(8) System Manager's Manual MII-DIAG(8)
NAME
mii-diag - Network adapter control and monitoring
SYNOPSIS
mii-diag [options]<interface>
DESCRIPTION
This manual page documents briefly the mii-diag network adapter control and monitoring command. Addition doc‐
umentation is available from http://scyld.com/diag/index.html.
This mii-diag command configures, controls and monitors the transceiver management registers for network
interfaces, and configures driver operational parameters. For transceiver control mii-diag uses the Media
Independent Interface (MII) standard (thus the command name). It also has additional Linux-specific controls
to communicate parameters such as message enable settings and buffer sizes to the underlying device driver.
The MII standard defines registers that control and report network transceiver capabilities, link settings and
errors. Examples are link speed, duplex, capabilities advertised to the link partner, status LED indications
and link error counters.
OPTIONS
The mii-diag command supports both single character and long option names. Short options use a single dash
(´-´) in front of the option character. For options without parameters, multiple options may be concatenated
after a single dash. Long options are prefixed by two dashes (´--´), and may be abbreviated with a unique
prefix. A long option may take a parameter of the form --arg=param or --arg param.
A summary of options is as follows.
-A, --advertise <speed|setting>
-F, --fixed-speed <speed|setting>
Speed is one of: 100baseT4, 100baseTx, 100baseTx-FD, 100baseTx-HD, 10baseT, 10baseT-FD, 10baseT-HD.
For more precise control an explicit numeric register setting is also allowed.
-a, --all-interfaces
Show the status of all interfaces. This option is not recommended with any other option, especially
ones that change settings.
-s,--status
Return exit status 2 if there is no link beat.
-D Increase the debugging level. This may be used to understand the actions the command is taking.
-g, --read-parameters
Show driver-specific parameters.
-G, --set-parameters value[,value...]
-? Emit usage information.
DESCRIPTION
Calling the command with just the interface name produces extensive output describing the transceiver capabil‐
ities, configuration and current status.
The '--monitor' option allows scripting link beat changes.
This option is similar to --watch, but with lower overhead and simplified output. It polls the interface only
once a second and the output format is a single line per link change with three fixed words
<unknown|down||negotiating|up> <STATUS> <PARTNER-CAP>
Example output: mii-diag --monitor eth0
down 0x7809 0x0000
negotiating 0x7829 0x45e1
up 0x782d 0x45e1
down 0x7809 0x0000
This may be used as
mii-diag --monitor eth0 |
while read linkstatus bmsr linkpar; do
case $linkstatus in
up) ifup eth0 ;;
down) ifdown eth0 ;;
esac
done
It may be useful to shorten the DHCP client daemon timeout if it does not receive an address by adding the
following setting to /etc/sysconfig/network: DHCPCDARGS="-t 3"
SEE ALSO
ether-wake(8),net-diag(8),mii-tool(8).
Addition documentation is available from http://scyld.com/diag/index.html.
KNOWN BUGS
The --all-interfaces option is quirky. There are very few settings that are usefully applied to all inter‐
faces.
AUTHOR
The manual pages, diagnostic commands, and many of the underlying Linux network drivers were written by Donald
Becker for the Scyld Beowulf(™) cluster system.
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