I've found a similar thread to this but he got no answer (thread 252374 - can't post URL in my message as I'm a new user):

I understand "ethtool" may not work or produce the correct output on some cards and the same goes for "mii-tool" and vice versa. Are there files I can access directly to be assured of the correct settings? For me, "mii-tool" seems to reporting correctly on a HP blade's NIC but "ethtool" reports differently (it runs, but reports the card running at half duplex or is not actually stating that when we run "ethtool eth1").

See below how mii-tool reports full duplex (which I forced after it dropped out once but that's another matter), but ethtool says half-duplex. I tried looking at a file under /proc and that also says half duplex.

Is there a file we can look at to be sure? I understand that the drivers play a big role in how accurate the output of most commands are but I was wondering what can be relied upon the most.

# mii-tool eth1
eth1: 100 Mbit, full duplex, link ok


# ethtool eth1
Settings for eth1:
Supported ports: [ MII ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Half 1000baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Half 1000baseT/Full
Advertised auto-negotiation: Yes
Speed: 100Mb/s
Duplex: Half
Port: Twisted Pair
PHYAD: 1
Transceiver: internal
Auto-negotiation: on
Supports Wake-on: g
Wake-on: d
Current message level: 0x000000ff (255)
Link detected: yes


# cat /var/spool/compaq/nic/nicinfo/eth1.info
Description Broadcom Corporation NetXtreme BCM5703 Gigabit
Ethernet (rev 10)
Driver_Name tg3
Driver_Version 3.10RH
PCI_Vendor 0x14e4
PCI_Device_ID 0x16c7
PCI_Subsystem_Vendor 0x0e11
PCI_Subsystem_ID 0x00cb
PCI_Revision_ID 0x10
PCI_Bus 5
PCI_Slot 2
IRQ 72
System_Device_Name eth1
Current_HWaddr 00:12:79:3B0:9B

Link Up
Speed 100
Duplex Half
State up
Auto_Negotiate on


Rx_Errors 0
Tx_Errors 0


Tx_Abort_Late_Coll 0
Tx_Deferred_Ok 17932295
Rx_Align_Errors 0

ethtool superseeds miitool. notice that mii-tool can only report up to 100MBit, while ethtool is aware of the gigabit concept, and knows how to look at a greater range of hardware.

Thanks for that but at the end of the day I want what can report the most basic NIC settings correctly only. Whilst the speed is one of those, the duplex is just as important, and in this case 'ethtool' seems to be reporting half duplex incorrectly. Are there files or specific dirs I can get these off directly? I take it these tools are pretty low level and grab the info through specific drivers?

Looking at some of my systems with tg3 card, i can verify that 1) ethtool reports correctly, and 2) mii-tool does not.

i suggest using either a newer version of the software, updating your tg3 module/driver, and verifying you switch / router really is serving you full duplex.

AFAIK these tools attempt to talk through the driver to the card to get their info, but if you need to know how exactly it does it i suggest looking at the source directly or the kernel dev mail list, provided google.com/linux doesn't give you all the answers you seek.