How to view my network card is working in correct speed in Linux

[senthil_kumar_1]

Hi All,

I have four 1Gbps network card on my RHEL 5.3.

And they are connected with 1GB switch port.

But when checked the working speed by the command "mii-tools" it is showing as 100BaseTx-FD , so I believe it is working at 100Mbps.

Example:

# mii-tool
eth0: negotiated 100baseTx-FD, link ok
eth1: negotiated 100baseTx-FD, link ok
eth2: no link
eth3: no link


The I checked the network card status by "ethtoo".

# ethtool eth0
Settings for eth0:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Advertised auto-negotiation: Yes
Speed: 1000Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 1
Transceiver: internal
Auto-negotiation: on
Supports Wake-on: g
Wake-on: g
Link detected: yes


In above output it is showing following details.

Advertised auto-negotiation: Yes
Speed: 1000Mb/s
Duplex: Full
Port: Twisted Pair


In mii-tools, it is showing 100baseTx-FD and in ethtoos, it is howing "Speed: 1000Mb/s".

1)What is difference between the outputs of mii-tools and ethtool?

2)what is the currect working speed of the NIC in that server?

[Matti_Kurkela · Accepted solution]

1.)
"mii-tool" was originally developed to get information from the Media Independent Interface of 100 Mbit NICs.

http://en.wikipedia.org/wiki/Media_Independent_Interface

When the gigabit NICs were designed, the MII interface was replaced by other solutions. Most Linux NIC drivers for gigabit NICs still offer an emulation of the MII interface, in case some application wants to query the link state using the MII methods. However, the MII hardware interface, and this emulation, cannot describe any speeds faster than 100 Mbps.

The ethtool API in the kernel was specifically designed to be extensible and independent of any particular hardware implementation.

You should always prefer ethtool over mii-tool, and use mii-tool only if ethtool does not work with your NIC driver.

2.)
The speed of your eth0 NIC is 1000 Mbps, full duplex.

MK

[wobbe]

I've seen the same issue on all RHEL 5 based server that we own. Ethtool is reporting the correct speed. You can probably check this on you switch. I would not use mii-tool on RHEL based systems.