IP Addresses and the ip Command in Linux

1. What Is an IP Address?

An IP (Internet Protocol) address uniquely identifies a device on a network. In Linux, IP addresses are used for internet access, local communication, and configuring services.

IPv4: Four numerical segments (e.g., 192.168.1.1)
IPv6: Eight hexadecimal blocks designed to expand the address pool

2. What Is the ip Command?

ip is the modern replacement for ifconfig, used for inspecting and manipulating network interfaces, IP addresses, routes, and device status.

ip addr

ip link

ip route

3. Installing ifconfig (Legacy Tool)

ifconfig is part of the deprecated net-tools package. To install:

sudo apt install net-tools      # Debian / Ubuntu

sudo yum install net-tools      # CentOS / RHEL

4. ip vs ifconfig Comparison

Feature	ifconfig	ip
Show IP address	`ifconfig`	`ip addr`
Modern & extensible	❌	✅
Interface control	`ifconfig eth0 down`	`ip link set eth0 down`
View routing table	`route -n`	`ip route`

5. Useful ip Subcommands

View all addresses:
```
ip addr show
```
IPv4 only:
```
ip -4 addr show
```
IPv6 only:
```
ip -6 addr show
```
Show routes:
```
ip route show
```
Display network interfaces:
```
ip link show
```

6. Check IP with hostname Command

Quickly show current IP(s):

hostname -I

7. Temporarily Assign an IP Address

Manually assign IPv4 address to eth0:

sudo ip addr add 192.168.1.10/24 dev eth0

sudo ip link set eth0 up

8. Security and Usage Notes

Private IPs (e.g., 192.168.x.x) are for local networks
Public IPs require careful firewall and NAT configuration
DHCP and VPN settings affect routing and IP assignment

9. Conclusion

Mastering IP configuration and the ip command in Linux is foundational for networking. Whether viewing interfaces, configuring addresses, or inspecting routing behavior, these tools help users maintain control over system connectivity in both local and enterprise environments.