Viewing and changing netword card setting
Checking our network card current setting
There are two commands that we can use to check our current network card setting. The first command is “mii-tool”, it has been around almost since the beginning of Linux and will be depreciated in the future version of Linux. If we don’t specify any parameter to the “mii-tool” command, we will get one line of information per network card. It will display the current speed of the network card, the duplex mode it’s using and if you have a link or not. If we don’t have a link up (no link) and it is suppose to be, I suggest to verify that your cable is connected to the server and that the port on the network switch is activate. If this is the case, you may want to try another network cable and see if the link come up.
# mii-tool eth0: 100 Mbit, full duplex, link ok eth1: 100 Mbit, full duplex, no link #
If we add the verbose parameter (-v), we will get some additional information about each network card.
# mii-tool -v eth0: 100 Mbit, full duplex, link ok product info: vendor 00:aa:00, model 50 rev 0 basic mode: 100 Mbit, full duplex basic status: link ok capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control eth1: 100 Mbit, full duplex, no link product info: vendor 00:10:18, model 23 rev 6 basic mode: 100 Mbit, full duplex basic status: no link capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control #
I would suggest using the “ethtool” command instead of the depreciated “mii-tool”. The “mii-tool” may not work with some of the newer network card and may be excluded from future version of RedHat/Centos/Fedora. With the “ethtool” command, we need to specify the name of the interface that we want to see the current state. In all of our example, we will use the interface “eth0″.
# 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: No Speed: 100Mb/s Duplex: Full Port: MII PHYAD: 1 Transceiver: internal Auto-negotiation: off Supports Wake-on: g Wake-on: g Current message level: 0x00000007 (7) Link detected: yes #
Display driver information
If we want to see some driver information about our network card, use the “-i” parameter next to the “ethtool” command.
In this example, we can see that the driver we are using for this card is “e100″. Effectively, if we use the “lsmod” (list module) we found out the the “e100″ is actually loaded.
# ethtool -i eth0 driver: e100 version: 3.5.10-k2-NAPI firmware-version: N/A bus-info: 0000:05:08.0 # # lsmod | grep e100 e100 36809 0 mii 9409 2 3c59x,e100 #
Display statistics information
With the “-S” parameter, we can display statistics about our network card.
This information could be valuable if you are experimenting some problem with that interface. It will confirm your doubt or it will indicate that you should check somewhere else to identify the problem.
# ethtool -S eth0
NIC statistics:
rx_packets: 12684
tx_packets: 7638
rx_bytes: 14990414
tx_bytes: 621100
rx_errors: 8
tx_errors: 0
rx_dropped: 0
tx_dropped: 0
multicast: 0
collisions: 0
rx_length_errors: 7
rx_over_errors: 0
rx_crc_errors: 1
rx_frame_errors: 0
rx_fifo_errors: 0
rx_missed_errors: 0
tx_aborted_errors: 0
tx_carrier_errors: 0
tx_fifo_errors: 0
tx_heartbeat_errors: 0
tx_window_errors: 0
tx_deferred: 0
tx_single_collisions: 0
tx_multi_collisions: 0
tx_flow_control_pause: 0
rx_flow_control_pause: 0
rx_flow_control_unsupported: 0
tx_tco_packets: 0
rx_tco_packets: 0
#
Network adapter self test
You can also run a self test on the network card. Beside the interface name you can specify two types of tests: offline (default) means to perform full set of tests possibly causing normal operation interruption during the tests, online means to perform limited set of tests do not interrupting normal adapter operation.
# ethtool -t eth0 online The test result is PASS The test extra info: Link test (on/offline) 0 Eeprom test (on/offline) 0 Self test (offline) 0 Mac loopback (offline) 0 Phy loopback (offline) 0 # ethtool -t eth0 offline The test result is PASS The test extra info: Link test (on/offline) 0 Eeprom test (on/offline) 0 Self test (offline) 0 Mac loopback (offline) 0 Phy loopback (offline) 0 #
Changing network card setting interactively
Below we change the network card setting from the command line. I strongly recommend doing these changes on the console, if not you may loose your network connection with the your server.
In this example we will set the interface “eth0″ speed to 10Mb/s and the duplex mode to half. After doing the change we use again the “ethtool” command to verify that our change have took place.
# ethtool -s eth0 speed 10 duplex half # 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: No Speed: 10Mb/s Duplex: Half Port: MII PHYAD: 1 Transceiver: internal Auto-negotiation: off Supports Wake-on: g Wake-on: g Current message level: 0x00000007 (7) Link detected: yes #
We will now set back our network card speed back to 100Mb/s, the duplex mode to “Full” and activate the speed autonegociate.
Again we verify that our change have took place by issuing the “ethtool -s eth0″ command.
# ethtool -s eth0 speed 100 duplex full autoneg on # 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: 100baseT/Full Advertised auto-negotiation: Yes Speed: 100Mb/s Duplex: Full Port: MII PHYAD: 1 Transceiver: internal Auto-negotiation: on Supports Wake-on: g Wake-on: g Current message level: 0x00000007 (7) Link detected: yes #
Setting speed and duplex at boot time
If we want to set the network card setting permanently, so they are preserve even after rebooting the the server, we need to open the file:
# vi /etc/sysconfig/network-scripts/ifcfg-eth0
Append following line:
ETHTOOL_OPTS="speed 100 duplex full autoneg off"
If you want that change to become effective now, you will need to restart the network service. Be aware that people and/or processes running on the system may be affected by this restart.
# service network restart
Hoping this article will be prove to be useful and see you soon.
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