Linux IP Routing

Linux IP Routing Guide

Complete beginner-friendly guide to IP routing on Linux, covering Arch Linux, CachyOS, and other distributions including routing tables, static routes, and network routing configuration.

---

Table of Contents

1. Routing Tables
2. Static Routes
3. Routing Configuration
4. Troubleshooting

---

Routing Tables

View Routes

List routes:

# List routes
ip route show

# Or
route -n

# Show routing table
ip route list

# Show default route
ip route show default

What it shows:

• Destination networks
• Gateway addresses
• Interface used
• Route metrics

Understanding Routes

Route format:

192.168.1.0/24 via 192.168.1.1 dev eth0

Components:

• 192.168.1.0/24: Destination network
• via 192.168.1.1: Gateway (router)
• dev eth0: Network interface

---

Static Routes

Add Route

Add static route:

# Add route
sudo ip route add 192.168.2.0/24 via 192.168.1.1

# Add with interface
sudo ip route add 192.168.2.0/24 via 192.168.1.1 dev eth0

# Add default route
sudo ip route add default via 192.168.1.1

What it does:

• Routes traffic for specific network through gateway
• Useful for multiple networks or VPNs
• Temporary (lost on reboot)

Delete Route

Remove route:

# Delete route
sudo ip route del 192.168.2.0/24

# Delete default route
sudo ip route del default

---

Routing Configuration

Persistent Routes

Make permanent (systemd-networkd):

# Create route file
sudo vim /etc/systemd/network/route-eth0

Add:

[Route]
Destination=192.168.2.0/24
Gateway=192.168.1.1

Using NetworkManager:

# Edit connection
nmcli connection edit "Wired connection 1"

# Add route
set ipv4.routes "192.168.2.0/24 192.168.1.1"
save
activate

Route Metrics

Set route priority:

# Add route with metric
sudo ip route add 192.168.2.0/24 via 192.168.1.1 metric 100

# Lower metric = higher priority

---

Troubleshooting

Routing Issues

Check routing:

# Check routes
ip route show

# Test connectivity
ping -r 192.168.2.1

# Trace route
traceroute 192.168.2.1

# Check gateway
ip route get 192.168.2.1

Default Route Missing

Fix default route:

# Add default route
sudo ip route add default via 192.168.1.1

# Check gateway
ip route show default

---

Summary

This guide covered IP routing for Arch Linux, CachyOS, and other distributions, including routing tables, static routes, and configuration.

---

Next Steps

• Networking - Network setup
• Network Utilities - Network tools
• ArchWiki Routing: https://wiki.archlinux.org/title/Network_configuration#Routing_table

---

This guide covers Arch Linux, CachyOS, and other Linux distributions. For distribution-specific details, refer to your distribution's documentation.