ifconfig Command Guide: Checking and Configuring Network Interface Information (Legacy)

Overview of ifconfig

`ifconfig` stands for 'interface configurator' and has long been used to manage network interfaces connected to the system. However, it is being replaced by the `ip` command from the `iproute2` toolset due to lack of IPv6 support, difficulty in complex scripting, and more.

Main Functions of ifconfig

`ifconfig` command is primarily used for the following purposes:

Key Use Cases (Past and Some Systems)

Check Network Interface Status: Displays the IP address, subnet mask, MAC address, etc., of each interface.
Check Network Statistics: Shows the number of packets sent and received, errors, collisions, etc., per interface.
Activate/Deactivate Interface: Used to turn a specific network interface on or off.
Set IP Address: Assigns or changes the IP address for an interface.

`ifconfig` vs `ip`

`ifconfig` is still used in some older systems or specific environments, but new feature development has stopped, and `ip` has completely replaced its role.

ifconfig: Legacy tool, lacks IPv6 support, limited functionality.
ip: Modern and powerful, fully supports IPv6, provides various advanced features like routing and tunneling.

Installing ifconfig (Optional)

Some recent Linux distributions (e.g., from Ubuntu 18.04+) may not have `ifconfig` installed by default. If necessary, you can install the `net-tools` package to use it.

Install `ifconfig` (Debian/Ubuntu)

sudo apt update
sudo apt install net-tools

Command to install the `net-tools` package containing `ifconfig` on Debian or Ubuntu-based systems.

Key ifconfig Command Options

`ifconfig` command allows you to query network interfaces and perform basic configurations with a simple syntax. (Usually requires administrative privileges)

1. Information Query

2. Interface Configuration (Administrative Privileges Required)

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Description:

`ifconfig` Executes the command.

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Usage Examples

Learn how to check information about network interfaces and perform basic configurations through various examples of the `ifconfig` command.

Check Information of All Active Network Interfaces

ifconfig

Displays the IP addresses, MAC addresses, statistics, etc., of all active network interfaces (e.g., `eth0`, `lo`) on the current system.

Check Specific Interface (eth0) Information

ifconfig eth0

Displays detailed information for the network interface named `eth0`.

Activate Specific Interface

sudo ifconfig eth0 up

Activates (UP) the `eth0` interface. This command requires administrative privileges.

Set IP Address and Netmask for Interface

sudo ifconfig eth0 192.168.1.10 netmask 255.255.255.0

Sets the IP address `192.168.1.10` and netmask `255.255.255.0` for the `eth0` interface. (This is a temporary setting and may disappear upon reboot.)

Check Including All Inactive Interfaces

ifconfig -a

Displays information about all network interfaces, whether active or inactive. This can be useful for diagnosing problems.

Check Status of Loopback Interface (lo)

ifconfig lo

Checks the status of the `lo` (loopback) interface, which refers to the local system itself. This is used for local testing without a network connection.