Basic Network Concepts on Linux RHEL / CentOS 5&6

                                                                     

Here we are providing some idea about network and network commands

To check IP address and IP information

#ifconfig 

To set IP address

#setup

network configuration 

select ethernet

give IP address, subnet mask, gateway

close

quit

quit

#service network restart

To provide DNS information:

#vi /etc/resolv.conf

(type as follows)

nameserver (DNS IP)

ex: nameserver 202.138.103.100

save&quit

To check network connectivity:

Ping: packet internet gropher

#ping server IP

To check LAN card status:

#ping 127.0.0.1 

To check host name:

#hostname

To change host name:

#hostname (fqdn)

ex: #hostname station1.redhat.com

To assign new hostname permanently

#vi /etc/hosts 

add a new line 

<IP> <fqdn> <hostname>

ex:

192.168.0.1 station1.redhat.com station1

save&quit

#vi /etc/sysconfig/network

edit as follows

hostname=<fqdn>

ex:

hostname=station1.redhat.com

To view current version of kernel 

#uname -r

To view current run level:

#runlevel

we have 6 run levels:

runlevel 0=shutdown

runlevel 1=single user mode

runlevel 2=multi user without nfs

runlevel 3=multi user with network(only text mode)

runlevel 4=un used

runlevel 5=multi user with graphics & network

runlevel 6=reboot

#netstat -ant it will gives network statistics(which port number of the server is connected to which port number of client)

#vi /etc/sysconfig/network-scripts

this is the directory stores networking information 

#ifcfg-eth0

this command gives gateway, boot protocol, netmask details

this is the file which stores IP addresses and networking details

ifdown <eth0>:

this command is used to down the device

ifup <eth0>:

this command is used to bring the interface up device