Overview¶

Linux provides various commands to configure, monitor, and troubleshoot network settings. These commands are essential for:

Network configuration
Troubleshooting connectivity
Cybersecurity and reconnaissance
System administration

ifconfig — Network Interface Configuration¶

Description¶

ifconfig is used to view and configure network interfaces.

Basic Usage¶

ifconfig

Explanation
Displays all active network interfaces along with:

IP address
MAC address
Netmask
Broadcast address

Note¶

ifconfig is deprecated in modern systems
Replaced by ip command

ip addr — View IP Address¶

Description¶

Displays detailed information about network interfaces.

Usage¶

ip addr

Explanation

Shows:

IP addresses (IPv4 & IPv6)
Interface status (UP/DOWN)
MAC address

ip route — Routing Table¶

Description¶

Displays the system's routing table.

Usage¶

ip route show

Explanation

Shows:

Default gateway
Network routes
Interface used for routing

dhclient — Obtain IP Address¶

Description¶

dhclient requests an IP address from a DHCP server.

Usage¶

dhclient

Explanation

Automatically assigns IP address
Useful when network configuration fails

netstat — Network Statistics¶

Description¶

netstat displays network connections, ports, and statistics.

Basic Usage¶

netstat

Common Options¶

Routing Table¶

netstat -r

Network Interfaces¶

netstat -i

Protocol Statistics¶

netstat -s

Verbose Output¶

netstat -v

Show Process ID¶

netstat -p

TCP Connections¶

netstat -t

UDP Connections¶

netstat -u

Listening Ports¶

netstat -l

Combined Example¶

netstat -tulnp

Explanation

-t → TCP
-u → UDP
-l → listening ports
-n → numeric output (no DNS resolution)
-p → process ID

Netdiscover — Network Reconnaissance¶

Description¶

Netdiscover is used for ARP-based network discovery.

Usage¶

netdiscover -i eth0

Explanation

-i → specify network interface
Scans local network for active hosts
Useful in penetration testing

DNS Configuration¶

Edit DNS Server¶

vim /etc/resolv.conf

Explanation

Used to configure DNS servers manually
Example entry:

```id="p2s9xz" nameserver 8.8.8.8

---

## Check DNS Status

```bash
systemd-resolve --status

Explanation

Displays active DNS servers
Shows resolver configuration

Hosts File — Local DNS Mapping¶

Edit Hosts File¶

vim /etc/hosts

Explanation

Maps domain names to IP addresses locally
Used for:
- Blocking websites
- Testing domains
- Redirecting traffic

Example¶

```id="6k8w2r" 127.0.0.1 example.com

**Effect**

- Redirects `example.com` to localhost

- Can be used to block access


---

# Practical Examples

## Check Network Information

```bash
ip addr
ip route show

Check Open Ports¶

netstat -tulnp

Renew IP Address¶

dhclient

Discover Devices on Network¶

netdiscover -i wlan0

Important Notes¶

Root privileges may be required for some commands
Prefer ip over ifconfig in modern systems
Be cautious when editing /etc/resolv.conf and /etc/hosts
netdiscover should be used only in authorized environments

Summary Table¶

Command	Purpose
`ifconfig`	View/configure interfaces
`ip addr`	Show IP details
`ip route`	Show routing table
`dhclient`	Get IP via DHCP
`netstat`	Network connections and stats
`netdiscover`	Discover network hosts
`/etc/resolv.conf`	DNS configuration
`/etc/hosts`	Local domain mapping

Conclusion¶

These networking commands are essential for:

Network troubleshooting
System configuration
Cybersecurity reconnaissance

Mastering them provides strong control over Linux networking environments and is crucial for both administrators and security professionals.