Basic Networking Commands in Linux

Every node participating in networking needs a valid IP address. On Linux command prompt IP address is assigned by a network configuration window. This window can be invoked by selecting network configuration sub menu form setup command or directly executing system-config-network commands.



Run setup command form root user

 #setup 

this will launch a new window select network configuration



now a new window will show you all available LAN card select your LAN card ( if you don’t see any LAN card here mean you don’t have install driver)



assign IP in this box and click ok



click on ok, quit and again quit to come back on root prompt.
Alternately you can use system-config-network command directly to invoke this setup window

 #system-config-network 

whatever change you made in network configuration will not take place till you restart the LAN card

 #service network restart 

ifconfig

The ifconfig command will display the configuration of all active Ethernet card. Without specifying any parameter this command will show all active Ethernet card. if you want to see the configuration of any specific Ethernet card then use the name of that card as the command line arguments. for example to show the IP configuration on loop back Interface execute this command

 #ifconfig lo 

ifup/ifdown

Each installed network adapter has a corresponding ifcfg-* file in /etc/sysconfig/network-scripts. You can activate or deactivate that adapter with the ifup and ifdown commands. Either of the following commands will activate the eth0 network adapter:

 #ifup ifcfg-eth0 #ifup eth0 

netstat

The netstat program provides real-time information on the status of your network connections, as well as network statistics and the routing table. The netstat command has several options you can use to bring up different sorts of information about your network.

arp

The Address Resolution Protocol associates the hardware address of a network adapter with an IP address. The arp command (in the /sbin directory) displays a table of hardware and IP addresses on the local computer. With arp, you can detect problems such as duplicate addresses on the network, or you can manually add arp entries as required.

mii-tool

mii-tool command is used to check the link is activated or not. Most use of mii-tool command is to check to physical link of Ethernet card on command line. With this command you can check on command prompt that cable is plugged in LAN card or not.

ping

ping command is used to check the physical connectivity. If you get reply mean everything is ok. If you get request time out response means there is some problem it could be unplugged cable power off switch or enabled firewall on destination node. If you get Destination host unreachable means remote node is not in your network. Use CTRL+C to abort the ping sequence

service network restart

Whatever change you made in network configuration files will not take place until you restart the network services. To implement change this command is used.

Source Computer Networking Notes.

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