Wednesday, August 26, 2015

IFCONFIG Commands to Configure Network Interface in Linux

IFCONFIG -  Commands to Configure Network Interface in Linux


1. View All Network Setting

The “ifconfig” command with no arguments will display all the active interfaces details. The ifconfig command also used to check the assigned IP address of an server.


[root@tecmint ~]# ifconfig

eth0      Link encap:Ethernet  HWaddr 00:0B:CD:1C:18:5A
          inet addr:172.16.25.126  Bcast:172.16.25.63  Mask:255.255.255.224
          inet6 addr: fe80::20b:cdff:fe1c:185a/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2341604 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2217673 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:293460932 (279.8 MiB)  TX bytes:1042006549 (993.7 MiB)
          Interrupt:185 Memory:f7fe0000-f7ff0000

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:5019066 errors:0 dropped:0 overruns:0 frame:0
          TX packets:5019066 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:2174522634 (2.0 GiB)  TX bytes:2174522634 (2.0 GiB)

tun0      Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
          inet addr:10.1.1.1  P-t-P:10.1.1.2  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

2. Display Information of All Network Interfaces

The following ifconfig command with -a argument will display information of all active or inactive network interfaces on server. It displays the results for eth0, lo, sit0 and tun0.


[root@tecmint ~]# ifconfig -a

eth0      Link encap:Ethernet  HWaddr 00:0B:CD:1C:18:5A
          inet addr:172.16.25.126  Bcast:172.16.25.63  Mask:255.255.255.224
          inet6 addr: fe80::20b:cdff:fe1c:185a/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2344927 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2220777 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:293839516 (280.2 MiB)  TX bytes:1043722206 (995.3 MiB)
          Interrupt:185 Memory:f7fe0000-f7ff0000

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:5022927 errors:0 dropped:0 overruns:0 frame:0
          TX packets:5022927 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:2175739488 (2.0 GiB)  TX bytes:2175739488 (2.0 GiB)

sit0      Link encap:IPv6-in-IPv4
          NOARP  MTU:1480  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

tun0      Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
          inet addr:10.1.1.1  P-t-P:10.1.1.2  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

3. View Network Settings of Specific Interface

Using interface name (eth0) as an argument with “ifconfig” command will display details of specific network interface.
 
[root@tecmint ~]# ifconfig eth0

eth0      Link encap:Ethernet  HWaddr 00:0B:CD:1C:18:5A
          inet addr:172.16.25.126  Bcast:172.16.25.63  Mask:255.255.255.224
          inet6 addr: fe80::20b:cdff:fe1c:185a/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2345583 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2221421 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:293912265 (280.2 MiB)  TX bytes:1044100408 (995.7 MiB)
          Interrupt:185 Memory:f7fe0000-f7ff0000

4. How to Enable an Network Interface

The “up” or “ifup” flag with interface name (eth0) activates an network interface, if it is not in active state and allowing to send and receive information. For example, “ifconfig eth0 up” or “ifup eth0” will activate the eth0 interface.
 
[root@tecmint ~]# ifconfig eth0 up
OR
[root@tecmint ~]# ifup eth0

5. How to Disable an Network Interface

The “down” or “ifdown” flag with interface name (eth0) deactivates the specified network interface. For example, “ifconfig eth0 down” or “ifdown eth0” command deactivates the eth0 interface, if it is in active state.
 
[root@tecmint ~]# ifconfig eth0 down
OR
[root@tecmint ~]# ifdown eth0

6. How to Assign a IP Address to Network Interface

To assign an IP address to an specific interface, use the following command with an interface name (eth0) and ip address that you want to set. For example, “ifconfig eth0 172.16.25.125” will set the IP address to interface eth0.
 
root@tecmint ~]# ifconfig eth0 172.16.25.125

7. How to Assign a Netmask to Network Interface

Using the “ifconfig” command with “netmask” argument and interface name as (eth0) allows you to define an netmask to an given interface. For example, “ifconfig eth0 netmask 255.255.255.224” will set the network mask to an given interface eth0.
 
[root@tecmint ~]# ifconfig eth0 netmask 255.255.255.224

8. How to Assign a Broadcast to Network Interface

Using the “broadcast” argument with an interface name will set the broadcast address for the given interface. For example, “ifconfig eth0 broadcast 172.16.25.63” command sets the broadcast address to an interface eth0.
 
[root@tecmint ~]# ifconfig eth0 broadcast 172.16.25.63

9. How to Assign a IP, Netmask and Broadcast to Network Interface

To assign an IP address, Netmask address and Broadcast address all at once using “ifconfig” command with all arguments as given below.
 
[root@tecmint ~]# ifconfig eth0 172.16.25.125 netmask 255.255.255.224 broadcast 172.16.25.63

10. How to Add New Alias to Network Interface

The ifconfig utility allows you to configure additional network interfaces using alias feature. To add alias network interface of eth0, use the following command. Please note that alias network address in same sub-net mask. For example, if your eth0 network ip address is 172.16.25.125, then alias ip address must be 172.16.25.127.
 
[root@tecmint ~]# ifconfig eth0:0 172.16.25.127

Next, verify the newly created alias network interface address, by using “ifconfig eth0:0” command.
 
[root@tecmint ~]# ifconfig eth0:0

eth0:0    Link encap:Ethernet  HWaddr 00:01:6C:99:14:68
          inet addr:172.16.25.123  Bcast:172.16.25.63  Mask:255.255.255.240
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:17

11. How to Remove Alias to Network Interface

If you no longer required an alias network interface or you incorrectly configured it, you can remove it by using the following command.
 
[root@tecmint ~]# ifconfig eth0:0 down

15. How to Change the MAC address of Network Interface

To change the MAC (Media Access Control) address of an eth0 network interface, use the following command with argument “hw ether“. For example, see below.
 
[root@tecmint ~]# ifconfig eth0 hw ether AA:BB:CC:DD:EE:FF

These are the most useful commands for configuring network interfaces in Linux, for more information and usage of ifconfig command use the manpages like “man ifconfig” at the terminal. Check out some other networking utilities below.
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