What would you use if you need to know the IP address of an interface on a Linux system?

What would you use if you need to know the IP address of an interface on a Linux system?

• ipconfig
• Read it in /etc/conf file
• show ip interface brief
• ifconfig 

EXPLANATION

Unix-like operating systems, ifconfig is used to configure, or view the configuration of, a network interface.

This document covers the GNU/Linux version of ifconfig.

Note

On modern Linux systems, the ip command has replaced ifconfig.

Description

ifconfig stands for "interface configuration." It is used to view and change the configuration of the network interfaces on your system.

Running the ifconfig command with no arguments, like this:

ifconfig

...displays information about all network interfaces currently in operation. The output will resemble the following:

eth0      Link encap:Ethernet  HWaddr 09:00:12:90:e3:e5  
          inet addr:192.168.1.29 Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::a00:27ff:fe70:e3f5/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:54071 errors:1 dropped:0 overruns:0 frame:0
          TX packets:48515 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:22009423 (20.9 MiB)  TX bytes:25690847 (24.5 MiB)
          Interrupt:10 Base address:0xd020 
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:83 errors:0 dropped:0 overruns:0 frame:0
          TX packets:83 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:7766 (7.5 KiB)  TX bytes:7766 (7.5 KiB)
wlan0     Link encap:Ethernet  HWaddr 58:a2:c2:93:27:36  
          inet addr:192.168.1.64  Bcast:192.168.2.255  Mask:255.255.255.0
          inet6 addr: fe80::6aa3:c4ff:fe93:4746/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:436968 errors:0 dropped:0 overruns:0 frame:0
          TX packets:364103 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:115886055 (110.5 MiB)  TX bytes:83286188 (79.4 MiB)

Here, eth0, lo and wlan0 are the names of the active network interfaces on the system.

• eth0 is the first Ethernet interface. (Additional Ethernet interfaces would be named eth1, eth2, etc.) This type of interface is usually a NIC connected to the network by a category 5 cable.
• lo is the loopback interface. This is a special network interface that the system uses to communicate with itself.
• wlan0 is the name of the first wireless network interface on the system. Additional wireless interfaces would be named wlan1, wlan2, etc.

These are the traditional naming conventions for network interfaces under Linux; other operating systems may have different names. For instance, under many BSD operating systems, Ethernet interfaces are named em0, em1, etc. Check your configuration, or consult your documentation, to determine the exact names of your interfaces.