To assign IP address - Tutorial

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 usethe 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 networkconnections,
as well as network statistics and the routing table.
The netstat command hasseveral 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 withan IP address.
The arp command (in the /sbin directory) displays a table
of hardware and IPaddresses 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.

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