route - Network Route Management Guide

Table of Contents

• Overview
• Basic Usage
• Route Management
• Gateway Configuration
• Network Interface Routes
• Advanced Options
• Troubleshooting
• Modern Alternatives
• Best Practices

Overview

route is a traditional command for viewing and manipulating the IP routing table. While considered legacy (replaced by ip route in modern systems), it’s still widely used and available.

Key Features

• Display routing table
• Add/delete routes
• Configure default gateway
• Interface routing
• Network management
• Static route configuration

Basic Usage

Display Routes

# Show routing table
route -n
 
# Show verbose output
route -v
 
# Show statistics
route -s

Basic Format

# General syntax
route [add|del] [-net|-host] target [netmask Nm] [gw Gw] [dev If]

Route Management

Add Routes

# Add network route
sudo route add -net 192.168.2.0 netmask 255.255.255.0 gw 192.168.1.1
 
# Add host route
sudo route add -host 192.168.2.10 gw 192.168.1.1
 
# Add default gateway
sudo route add default gw 192.168.1.1

Delete Routes

# Delete network route
sudo route del -net 192.168.2.0 netmask 255.255.255.0
 
# Delete host route
sudo route del -host 192.168.2.10
 
# Delete default gateway
sudo route del default

Gateway Configuration

Default Gateway

# Add default gateway
sudo route add default gw 192.168.1.1
 
# Add default gateway with metric
sudo route add default gw 192.168.1.1 metric 1
 
# Add gateway for specific network
sudo route add -net 192.168.2.0/24 gw 192.168.1.1

Multiple Gateways

# Add primary gateway
sudo route add default gw 192.168.1.1 metric 1
 
# Add secondary gateway
sudo route add default gw 192.168.1.2 metric 2

Network Interface Routes

Interface Specific Routes

# Add route via interface
sudo route add -net 192.168.2.0/24 dev eth0
 
# Add host route via interface
sudo route add -host 192.168.2.10 dev eth0
 
# Add default route via interface
sudo route add default dev eth0

Reject Routes

# Reject network
sudo route add -net 192.168.2.0/24 reject
 
# Reject host
sudo route add -host 192.168.2.10 reject

Advanced Options

Metrics and Flags

# Add route with metric
sudo route add -net 192.168.2.0/24 gw 192.168.1.1 metric 2
 
# Add route with specific flags
sudo route add -net 192.168.2.0/24 gw 192.168.1.1 mss 1400

Network Masks

# Using CIDR notation
sudo route add -net 192.168.2.0/24 gw 192.168.1.1
 
# Using netmask
sudo route add -net 192.168.2.0 netmask 255.255.255.0 gw 192.168.1.1

Troubleshooting

Common Issues

1. Gateway Unreachable

# Check gateway status
ping gateway_ip
 
# Verify interface status
ifconfig interface_name
 
# Check route table
route -n

2. Route Conflicts

# Show all routes
route -n
 
# Check specific network
route -n | grep network_address
 
# Verify metrics
route -n | sort -k 5

3. Interface Problems

# Check interface status
ifconfig interface_name
 
# Verify interface routes
route -n | grep interface_name

Modern Alternatives

IP Route Command

# Show routes (modern equivalent)
ip route show
 
# Add route
ip route add 192.168.2.0/24 via 192.168.1.1
 
# Delete route
ip route del 192.168.2.0/24
 
# Add default gateway
ip route add default via 192.168.1.1

Network Manager

# Show connections
nmcli connection show
 
# Modify route
nmcli connection modify "Connection Name" +ipv4.routes "192.168.2.0/24 192.168.1.1"
 
# Apply changes
nmcli connection up "Connection Name"

Best Practices

Route Management

# Document current routes
route -n > route_backup.txt
 
# Verify before changes
route -n | grep target_network
 
# Test after changes
ping destination_ip

Security Considerations

# Reject unwanted networks
sudo route add -net 10.0.0.0/8 reject
 
# Monitor route changes
watch -n 1 'route -n'
 
# Log route changes
route -n | logger

Quick Reference

Essential Commands

# Show routes
route -n
 
# Add network route
sudo route add -net network/mask gw gateway_ip
 
# Add host route
sudo route add -host host_ip gw gateway_ip
 
# Delete route
sudo route del -net network/mask

Common Options

-n    # Show numerical addresses
-v    # Verbose output
-net  # Network route
-host # Host route
gw    # Gateway
dev   # Interface

Example Configurations

Basic Network Setup

# Add default gateway
sudo route add default gw 192.168.1.1
 
# Add local network
sudo route add -net 192.168.1.0/24 dev eth0
 
# Add remote network
sudo route add -net 10.0.0.0/8 gw 192.168.1.254

Multiple Network Setup

# Primary route
sudo route add default gw 192.168.1.1 metric 1
 
# Secondary route
sudo route add default gw 192.168.1.2 metric 2
 
# Specific network route
sudo route add -net 192.168.2.0/24 gw 192.168.1.1

VPN Configuration

# Add VPN network
sudo route add -net 10.0.0.0/8 dev tun0
 
# Add VPN gateway
sudo route add default gw 10.0.0.1 metric 100
 
# Block direct access
sudo route add -net 192.168.2.0/24 reject

---

Remember:

• Always backup current routes
• Test changes carefully
• Document all modifications
• Consider using modern alternatives
• Monitor route changes
• Keep security in mind

For detailed information, consult the man pages (man route) and consider modern alternatives like ip route.