Determine the autonegotiated ethernet connection speed and duplex using the mii-tool command

by lifeLinux on May 2, 2011

Determine the autonegotiated ethernet connection speed and duplex using the mii-tool command. Running the following command as superuser with no options will generate basic information about all of the ethernet interfaces on the computer:

[[email protected] ~]# mii-tool


Sample outputs:

SIOCGMIIREG on eth0 failed: Input/output error
eth0: negotiated 100baseTx-FD, link ok

This output shows one interface (eth0) which was autonegotiated to 100 Mbps (100baseTx) and full duplex (FD).

Adding the -v option to the command generates verbose output and will tell you more information about the interface including the manufacturer and model. Type the following command:

[[email protected] ~]# mii-tool -v

Sample outputs:

SIOCGMIIREG on eth0 failed: Input/output error
eth0: negotiated 100baseTx-FD, link ok
  product info: vendor 00:50:43, model 11 rev 1
  basic mode:   autonegotiation enabled
  basic status: autonegotiation complete, link ok
  capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
  advertising:  100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control
  link partner: 100baseT4 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD

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