Setting your Linux NIC duplex and speeds

 1. NETWORK SETTINGS

A. To configure your network interfaces with ifconfig.

STATIC IP ADDRESS

#ifconfig interface_name ip_address netmask mask
 #ifconfig eth0 192.168.1.15 netmask 255.255.255.0 broadcast 192.168.1.255

To configure the default gateway:

#route add default gateway ip_address dev interface_name
 #route add default gateway 192.168.1.1 dev eth0

DYNAMIC IP ADDRESS

#dhclient interface
 #dhclient eth0
 Internet Systems Consortium DHCP Client V3.0.3
 Copyright 2004-2005 Internet Systems Consortium.
 All rights reserved.
 For info, please visit http://www.isc.org/products/DHCP
Listening on LPF/eth0/aa:00:11:22:33:44
 Sending on LPF/eth0/aa:00:11:22:33:44
 Sending on Socket/fallback
 DHCPREQUEST on eth0 to 255.255.255.255 port 67
 DHCPACK from 192.168.1.1
 bound to 192.168.1.130 -- renewal in 1002089 seconds.

SPEED AND DUPLEX MODE

To check your speed and duplex mode settings:

#ethtool interface_name
 #ethtool eth0
Settings for eth0:
          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

To set the duplex mode:

#ethtool interface_name -s duplex full|half autoneg off

To set the speed:

#ethtool interface_name -s 10|100|1000 autoneg off
 #ethtool eth0 -s speed 100 duplex full autoneg off

To restore the default speed and duplex mode settings to automatic negotiation:

#ethtool interface_name -s autoneg on
 #ethtool eth0 -s autoneg on

B. To configure your network interfaces with permanent settings.

The commands above will not be kept if you reboot your computer or restart the networking service. To keep your network settings permanently, open the /etc/network/interfaces file:

#vim /etc/network/interfaces
 STATIC IP ADDRESS
auto eth0
 iface eth0 inet static
     address 192.168.1.15
     netmask 255.255.255.0
     gateway 192.168.1.1

 

auto eth0
 iface eth0 inet dhcp
 SPEED, DUPLEX MODE & ROUTES
auto eth0
 iface eth0 inet static|dhcp
 post-up /usr/bin/ethtool eth0 -s speed 100 duplex full autoneg off
 post-up route add default gateway 192.168.1.1 dev eth0
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2. NETWORKING CHECKS

To see all your network interfaces settings:

#ifconfig -a

To check the settings of a particular interface:

#ifconfig interface
 #ifconfig eth0
 eth0    Link encap:Ethernet HWaddr AA:00:11:22:33:44
          inet addr:192.168.1.15 Bcast:192.168.1.255 Mask:255.255.255.0
          inet6 addr: fe80::a800:4ff:0000:000/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:1058 errors:0 dropped:0 overruns:0 frame:0
          TX packets:638 errors:0 dropped:0 overruns:0 carrier:0
          collisions:1 txqueuelen:1000
          RX bytes:100716 (98.3 KiB) TX bytes:86309 (84.2 KiB)
          Interrupt:169

To check your default gateway(s):

#route -n
 Kernel IP routing table
 Destination
 192.168.1.0
 0.0.0.0     Gateway
 0.0.0.0
 192.168.1.1     Genmask
 255.255.255.0
 0.0.0.0     Flags
 U
 UG     MSS
 0
 0     Window
 0
 0     irtt
 0
 0     Iface
 eth0
 eth0
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3. DNS (Domain Name System)

The domain name system (DNS), with name servers, translates domain names or FQDN to IP addresses.
For example, to access the openmaniak.com FQDN with a web browser such as Firefox, the website name is first translated into an IP address by a name server (DNS server).

The name servers IP addresses are stored in the /etc/resolv.conf file. If you get your IP address dynamically through a DHCP server, your name servers are generally automatically added in the file.

#vim /etc/resolv.conf
 nameserver 192.168.1.1

Where 192.168.1.1 is the name server IP address.
To see the name servers and the IP address – FQDN correspondence, use the dig command:

#dig openmaniak.com
 ; <<>> DiG 9.3.2 <<>> openmaniak.com
 ;; global options: printcmd
 ;; Got answer:
 ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 10055
 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
 ;openmaniak.com.                 IN   A
;; ANSWER SECTION:
 openmaniak.com.   76839   IN   A   84.16.81.23
;; Query time: 1 msec
 ;; SERVER: 192.168.1.1#53(192.168.1.1)
 ;; WHEN: Wed Apr 18 22:12:02 2007
 ;; MSG SIZE rcvd: 48

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4. PROXY

If you access the internet trough a proxy server, use the following settings:

#export HTTP_PROXY="http://login:password@proxy_address:proxy_port"
 #export FTP_PROXY="ftp://login:passowrd@proxy_address:proxy_port"
 To check your proxy settings:
#export | grep PROXY
 declare -x export HTTP_PROXY="http://login:password@proxy_address:proxy_port
 declare -x export FTP_PROXY="http://login:password@proxy_address:proxy_port

The settings configured above will be lost if you reboot your Linux.
So to configure the proxy settings permanently with the bash shell, proceed as follow:

To check the shell your are using:

#echo $SHELL
 /bin/bash

To access your user’s home directory:

#cd ~/

To add your proxy settings in the hidden “.bashrc” file:

#vim .bashrc
 export HTTP_PROXY="http://login:password@proxy_address:proxy_port"
 export FTP_PROXY="ftp://login:password@proxy_address:proxy_port"
 To check your proxy settings:
#cat ~/.bashrc ¦ grep PROXY
 export HTTP_PROXY="http://login:password@proxy_address:proxy_port"
 export FTP_PROXY="ftp://login:password@proxy_address:proxy_port"
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