Modern Linux Networking: Deprecating ifconfig for ip command

If you are typing ifconfig or netstat, you are living in the past (specifically, pre-2011). The Linux kernel has moved on to the netlink interface, and iproute2 is the standard approach.

1. Interface Management

• Old: ifconfig -a
• New: ip addr (or ip a)

To manage interfaces:

ip link set eth0 up
ip addr add 192.168.1.100/24 dev eth0

2. Routing Tables

• Old: route -n
• New: ip route (or ip r)

Understanding the route table is crucial. default via 192.168.1.1 dev eth0 means "If I don't know where to send this packet, send it to the router at 192.168.1.1".

3. Socket Statistics

• Old: netstat -tulpn
• New: ss -tulpn

ss is vastly faster because it queries the kernel directly instead of parsing /proc files.

• -t: TCP
• -u: UDP
• -l: Listening ports
• -p: Show process name (requires sudo)
• -n: Numeric ports (don't resolve DNS)

4. Network Namespaces

This is the technology behind Docker containers. ip lets you manage them directly.

# Create a namespace
ip netns add blue

# Run command inside namespace
ip netns exec blue ip a

The "blue" namespace has its own isolated network interfaces and routes. This is the foundation of container isolation.