ifconfig

Overview

The ifconfig (interface configuration) command is used to configure, control, and query network interface parameters. While newer systems prefer the ip command, ifconfig is still widely used for network interface management.

Syntax

ifconfig [interface] [options]

Common Options

Option	Description
`up`	Activate interface
`down`	Deactivate interface
`netmask addr`	Set netmask address
`broadcast addr`	Set broadcast address
`-a`	Display all interfaces
`mtu N`	Set MTU size
`metric N`	Set interface metric
`promisc`	Set/clear promiscuous mode

Key Use Cases

Configure network interfaces
View network interface status
Enable/disable interfaces
Set IP addresses
Troubleshoot network issues

Examples with Explanations

Example 1: View All Interfaces

ifconfig -a

Shows all network interfaces, including inactive ones

Example 2: Configure IP Address

ifconfig eth0 192.168.1.100 netmask 255.255.255.0

Sets IP address and netmask for eth0

Example 3: Enable/Disable Interface

ifconfig eth0 up
ifconfig eth0 down

Activates/deactivates the eth0 interface

Understanding Output

Standard output fields: - Interface name - Link status (UP/DOWN) - Hardware address (MAC) - IP address - Broadcast address - Netmask - MTU size - RX/TX statistics

Common Usage Patterns

Check interface status:
```
ifconfig eth0
```
Set temporary IP:
```
ifconfig eth0 192.168.1.100
```
Enable promiscuous mode:
```
ifconfig eth0 promisc
```

Performance Analysis

No real-time monitoring
Static configuration tool
Consider using ip command
Check interface statistics
Monitor packet errors

Additional Resources