Softpanorama (slightly skeptical) Open Source Software Educational Society

May the source be with you, but remember the KISS principle ;-) Softpanorama Search

ethtool

ethtool works with almost all NICs and permit checking and setting NIC speed as well as to force a multiple-speed NIC (such as 10/100Mbps, 100/1000Mbps, or 10/100/1000Mbps NIC) to one fixed and non-negotiable speed. Some network applications, such as ftp, might fails to work properly if NIC auto-negotiate speed with switch/router.  Try the following command on your machine to see the output.

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: 100Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 1
Transceiver: internal
Auto-negotiation: on
Supports Wake-on: g
Wake-on: d
Link detected: yes

ns2:/home/bezroun # ethtool eth1
Settings for eth1:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: Not reported
Advertised auto-negotiation: No
Speed: 100Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 1
Transceiver: internal
Auto-negotiation: off
Supports Wake-on: g
Wake-on: d
Link detected: yes

• Full Duplex - Setting that enables concurrent sending and receiving. This is usually desirable and enabled when your computer is connected to a switch. If can be autonegotiated of forced via ethtool.
•  Half Duplex - This settting requires a card to only send or receive at a single point of time. When your machine is connected to a Hub, it auto-negotiates itself and uses half duplex to avoid collisions.
• Auto-negotiation - This is the process of deciding whether to work in full duplex mode or half duplex mode. An ethernet card supporting autonegotiation will decide for itself which mode is the optimal one depending on the network it is attached to. As you can see eth0 here is autonegotiated and eth1 has authonegotiation turned off (useful for backup interfaces).

Note: If you want to find what type of network card is used, its speed, on which IRQ it is listed, and the chip type used, you use the following command : # dmesg |grep eth0
 

• There are three useful setting that permit getting information using ethtool:
   
  • ethtool -i eth0 display the first NIC driver setting.
  • ethtool -a eth0 displays information about autonegotiation
  • ethtool -S eth0 display information about speed and other parameters
     

Setting specific interface parameters with ethtool

To set specific parameters usually option -s is used:

• ethtool -s eth0 speed 100 duplex full autoneg off to force the first NIC to operate at fix and non-negotiable speed at 100Mbps full duplex.
   
• Note! In order to retain the change on each system reboot, append the following line in  file

  Red Hat directory/file:  /etc/sysconfig/network-scripts/ifcfg-eth0:

  • Parameter: ETHTOOL_OPTS="speed 100 duplex full autoneg off"

  Suse directory/file:  /etc/sysconfig/network (suse defines interfaces via MAC)

  • Parameter: ETHTOOL_OPTIONS='speed 100 duplex full autoneg off'
     

Old News

All about Linux Find the speed of your Ethernet card in Linux

For logging on to the net or for attaching as a node on a LAN, your computer needs a network card. The network card forms the interface between your computer and the network. There are different kinds of network cards available in the market depending on its speed and other features. Here is a tip to find out the characteristics of your network card.
 
 

If you want to find what type of network card is used, its speed, on which IRQ it is listed, and the chip type used, you use the following command :
 

# dmesg |grep eth0

Here eth0 is the first network card. If you have additional cards, it will be named eth1, eth2 and so on. And here is the output of the above command :
 

divert: allocating divert_blk for eth0
eth0: RealTek RTL8139 at 0xd800, 00:80:48:34:c2:84, IRQ 9
eth0:  Identified 8139 chip type 'RTL-8100B/8139D'
divert: freeing divert_blk for eth0
divert: allocating divert_blk for eth0
eth0: RealTek RTL8139 at 0xd800, 00:90:44:34:a5:33, IRQ 9
eth0:  Identified 8139 chip type 'RTL-8100B/8139D'
eth0: link up, 100Mbps, full-duplex, lpa 0x41E1
eth0: no IPv6 routers present
...

The important things to note here are those highlighted in colour. As you can see from the above listing, my ethernet card is a RealTek RTL8139 chipset based card on IRQ 9 (Interrupt Request). Its speed is 100 Mbps and is a full-duplex card. And the link is up.
 

As is the philosophy of Linux, there is more than one way of finding the same information. Linux also comes with a cute sounding tool called mii-tool which can also be used to get the same information about your network card.
 

# mii-tool -v eth0

eth0: negotiated 100baseTx-FD, link ok
product info: vendor 00:00:00, model 0 rev 0
basic mode:   autonegotiation enabled
basic status: autonegotiation complete, link ok
capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD
             10baseT-HD
...

Here -v is verbose mode. From the above listed output, one can see that the ethernet card is working as a 100baseTX, FD (Full Duplex) card which can work in the following modes :
 

• 100 Mbps Speed (Full duplex or half duplex ) or
• 10 Mbps speed (Full duplex or half duplex).
   

And it uses autonegotiation to bring up the link. You can call the above device as a 10/100 NIC.
 

Another tool which also does the same thing is ethtool. Try the following command on your machine to see the output.
 

# ethtool eth0

Settings for eth0:
  Supported ports: [ TP MII ]
  Supported link modes:   10baseT/Half 10baseT/Full
                          100baseT/Half 100baseT/Full
  Supports auto-negotiation: Yes
  Advertised link modes:  10baseT/Half 10baseT/Full
                          100baseT/Half 100baseT/Full
  Advertised auto-negotiation: Yes
  Speed: 100Mb/s
  Duplex: Full
  Port: MII
  PHYAD: 32
  Transceiver: internal
  Auto-negotiation: on
  Supports Wake-on: pumbg
  Wake-on: p
  Current message level: 0x00000007 (7)
  Link detected: yes

Here full duplex, half duplex and auto-negotiation have the following meanings.
 

Full Duplex - Logic that enables concurrent sending and receiving. This is usually desirable and enabled when your computer is connected to a switch.
 

Half Duplex - This logic requires a card to only send or receive at a single point of time. When your machine is connected to a Hub, it auto-negotiates itself and uses half duplex to avoid collisions.
 

Auto-negotiation - This is the process of deciding whether to work in full duplex mode or half duplex mode. An ethernet card supporting autonegotiation will decide for itself which mode is the optimal one depending on the network it is attached to.

Task: Install mii-tool and ethtool tools

If you are using Debian Linux you can install both of these package with following command:# apt-get install ethtool net-toolsIf you are using Red Hat Enterprise Linux you can install both of these package with following command:# up2date ethtool net-toolsIf you are using Fedora Core Linux you can install both of these package with following command:# yum install ethtool net-tools

Task: Get speed and other information for eth0

Type following command as root user:
# ethtool eth0Output:

Settings for eth0:
     Supported ports: [ TP MII ]
     Supported link modes:   10baseT/Half 10baseT/Full
                             100baseT/Half 100baseT/Full
     Supports auto-negotiation: Yes
     Advertised link modes:  10baseT/Half 10baseT/Full
                             100baseT/Half 100baseT/Full
     Advertised auto-negotiation: Yes
     Speed: 100Mb/s
     Duplex: Full
     Port: MII
     PHYAD: 32
     Transceiver: internal
     Auto-negotiation: on
     Supports Wake-on: pumbg
     Wake-on: d
     Current message level: 0x00000007 (7)
     Link detected: yes

Or use mii-tool command as follows:# mii-tool eth0Output:

eth0: negotiated 100baseTx-FD flow-control, link ok

Task: Change the speed and duplex settings

Setup eth0 negotiated speed with mii-tool
Disable autonegotiation, and force the MII to either 100baseTx-FD, 100baseTx-HD, 10baseT-FD, or 10baseT-HD:# mii-tool -F 100baseTx-HD
# mii-tool -F 10baseT-HDSetup eth0 negotiated speed with ethtool# ethtool -s eth0 speed 100 duplex full
# ethtool -s eth0 speed 10 duplex halfTo make these settings permanent you need to create a shell script and call from /etc/rc.local (Red Hat) or if you are using Debian create a script into the directory /etc/init.d/ directory and run update-rc.d command to update the script.

Read man page of mii-tool and ethtool for more information.