using ifconfig command

Ifconfig  is  used to configure the kernel-resident network interfaces. It is used at boot time to set up interfaces as necessary.  After that,it  is  usually  only  needed  when  debugging or when system tuning is needed. The ifconfig command simply is used for displaying current network configuration information, setting up an ip address along with netmask or broadcast address to network interface, creating an alias for network interface as well setting up hardware address and enable or disable network interfaces.

Here is basic usages of ifconfig command based on  scenario 

Ø  To view all activated  network interfaces

root@server-82:~# ifconfig 

Ø  To view the all network interface

root@server-82:~# ifconfig -a

Ø  3. To view specific network interface

root@server-82:~# ifconfig eth0

Ø  4. How to enable/disable network interface

root@server-82:~# ifconfig eth0 up or ifup eth0

root@server-82:~# ifconfig eth0 down or ifdown eth0

Ø   To assign a Ip address/netmask to network interface

 root@server-82:~# ifconfig eth0 10.10.10.1 netmask 255.255.255.0

Please note that the previous ip address of network interface will overlapped
           with this new ip address assigned and is will temporarily assigned. If you donot want to change in its network configuration file for permanently assigned, you can put it in /etc/rc.local file for startup automatic ip address setup.

Ø  To assign a broadcast address

 root@server-82:~# ifconfig eth0 broadcast 10.10.10.255

Ø  To change MTU for an network interface

root@server-82:~# ifconfig eth0 mtu 1454

Ø  To enable/disable promiscuous mode

 
Generally when a packet is received by a network card, it verifies whether the packet belongs to itself or not, if not then it drops the packet however in promiscuous mode, the network card will accept all the packets passed through it.

root@server-82:~# ifconfig eth0 promisc (for enable)
root@server-82:~# ifconfig eth0 –promisc ( for disable)

Ø  To add/remove new alias to network interface

             The alias is needed when we need multiple range of ips in single interface or
             when you are making your network interface using as trunk for manageable switch.

root@server-82:~# ifconfig eth0:0  10.11.11.1 netmask 255.255.255.0

           root@server-82:~# ifconfig eth0:0 down ( To remove the alias)

Ø  To change mac address of network interface

 
root@server-82:~# ifconfig eth0 hw ether AA:BB:CC:DD:EE:FF