How to Add Floating IP to Ubuntu and Debian Servers with Netplan

Floating IP addresses provide high availability and seamless failover capabilities for Linux servers. This comprehensive guide demonstrates how to configure floating IPs on Ubuntu and Debian systems using Netplan, enabling automatic IP migration between servers for improved reliability and redundancy.

Prerequisites for Floating IP Configuration

Before configuring floating IPs on your Ubuntu or Debian server, ensure you have the following requirements for successful implementation:

• Ubuntu 18.04+ or Debian 9+: Modern distributions with Netplan support
• Root or Sudo Access: Administrative privileges for network configuration
• Available Floating IP: A secondary IP address allocated by your hosting provider
• Network Interface Access: Understanding of your server’s network interface names
• Backup Configuration: Always backup existing network configs before changes

Understanding Floating IPs and Netplan

Floating IPs are virtual IP addresses that can be moved between servers without changing DNS records or requiring manual reconfiguration. Netplan is Ubuntu’s network configuration tool that uses YAML files to define network settings.

What Are Floating IPs?

• High Availability: Enable automatic failover between servers
• Load Balancing: Distribute traffic across multiple instances
• Zero Downtime: Switch services without DNS propagation delays
• Disaster Recovery: Quick recovery from server failures

Netplan Configuration Benefits

• Declarative Configuration: YAML-based, human-readable format
• Backend Agnostic: Works with NetworkManager and systemd-networkd
• Validation: Built-in configuration validation before applying
• Consistent: Standardized across Ubuntu distributions

Step-by-Step Floating IP Configuration

Follow this comprehensive guide to configure floating IPs using Netplan on Ubuntu and Debian systems. Each step includes validation commands to ensure proper setup.

Step 1: Identify Your Network Interface

First, identify your primary network interface name and current IP configuration.

# List all network interfaces
ip addr show

# Check current network configuration
ip route show

# View existing Netplan configuration
ls -la /etc/netplan/
cat /etc/netplan/*.yaml

Step 2: Create Floating IP Netplan Configuration

Create a new Netplan configuration file specifically for your floating IP address. This keeps the configuration organized and easily manageable.

# Create a new Netplan configuration file
sudo nano /etc/netplan/01-floating.yaml

Add the following configuration to the file:

network:
  version: 2
  ethernets:
    eth0:  # Replace with your actual interface name
      dhcp4: true  # Keep main IP from DHCP
      addresses:
        - 10.0.0.8/32  # Your floating IP address
      routes:
        - to: 10.0.0.8/32
          via: 0.0.0.0
          scope: link

Step 3: Validate and Apply Netplan Configuration

Before applying the configuration, validate it to prevent network connectivity issues.

# Test the Netplan configuration
sudo netplan try

# If validation passes, apply the configuration
sudo netplan apply

# Verify the floating IP is configured
ip addr show eth0
ip route show

Step 4: Manual IP Configuration Method (Alternative)

For temporary or testing purposes, you can also configure floating IPs manually using ip commands.

# Add floating IP to interface
sudo ip addr add 5.161.24.41/32 dev eth0

# Add route for the floating IP
sudo ip route add 5.161.24.41/32 dev eth0

# Verify configuration
ip addr show eth0
ip route show | grep 5.161.24.41

Step 5: Enable IP Forwarding (Optional)

If your server acts as a router or gateway, enable IP forwarding to allow traffic routing between interfaces.

# Enable IP forwarding temporarily
sudo sysctl net.ipv4.ip_forward=1

# Make IP forwarding permanent
echo 'net.ipv4.ip_forward=1' | sudo tee -a /etc/sysctl.conf

# Apply sysctl changes
sudo sysctl -p

# Verify IP forwarding is enabled
cat /proc/sys/net/ipv4/ip_forward

Advanced Floating IP Configuration

Learn advanced techniques for managing multiple floating IPs and complex network setups.

Multiple Floating IPs Configuration

Configure multiple floating IP addresses on a single interface for high-availability setups.

# Advanced Netplan configuration with multiple floating IPs
network:
  version: 2
  ethernets:
    eth0:
      dhcp4: true
      addresses:
        - 10.0.0.8/32    # First floating IP
        - 10.0.0.9/32    # Second floating IP
        - 10.0.0.10/32   # Third floating IP
      routes:
        - to: 10.0.0.8/32
          via: 0.0.0.0
          scope: link
        - to: 10.0.0.9/32
          via: 0.0.0.0
          scope: link
        - to: 10.0.0.10/32
          via: 0.0.0.0
          scope: link

VLAN-Based Floating IP Configuration

Configure floating IPs on VLAN interfaces for network segmentation.

# VLAN configuration with floating IP
network:
  version: 2
  ethernets:
    eth0:
      dhcp4: true
  vlans:
    eth0.100:
      id: 100
      link: eth0
      addresses:
        - 192.168.100.10/24
        - 192.168.100.50/32  # Floating IP on VLAN

Floating IP with Static Routes

Add custom routing rules for floating IP traffic management.

# Advanced routing configuration
network:
  version: 2
  ethernets:
    eth0:
      dhcp4: true
      addresses:
        - 10.0.0.8/32
      routes:
        - to: 10.0.0.8/32
          via: 0.0.0.0
          scope: link
        - to: 10.0.0.0/24
          via: 10.0.0.1
          metric: 100

Troubleshooting Floating IP Issues

Comprehensive solutions for common problems encountered when configuring floating IPs.

Common Issues and Solutions

• Netplan Apply Fails: Check YAML syntax and indentation
• IP Not Accessible: Verify routing and firewall rules
• Configuration Lost After Reboot: Ensure Netplan files are properly saved
• Interface Not Found: Confirm correct interface name with ip addr
• DHCP Conflicts: Check for IP address conflicts with DHCP range

Diagnostic Commands

# Check Netplan configuration syntax
sudo netplan --debug try

# View detailed network information
ip addr show
ip route show table all

# Test connectivity to floating IP
ping -I eth0 10.0.0.8

# Check ARP table
arp -a

# Monitor network traffic
sudo tcpdump -i eth0 host 10.0.0.8

# Check systemd-networkd status
sudo systemctl status systemd-networkd

# View network logs
journalctl -u systemd-networkd

Emergency Recovery Procedures

If network configuration causes connectivity issues, use these recovery methods:

# Reset to DHCP-only configuration
sudo rm /etc/netplan/01-floating.yaml
sudo netplan apply

# Manually restore network connectivity
sudo dhclient eth0

# Restart networking services
sudo systemctl restart systemd-networkd
sudo systemctl restart systemd-resolved

# Emergency network reset
sudo ip addr flush dev eth0
sudo dhclient eth0

Monitoring and Automation

Implement monitoring and automation for floating IP management in production environments.

Floating IP Health Check Script

#!/bin/bash
# floating-ip-monitor.sh

FLOATING_IP="10.0.0.8"
INTERFACE="eth0"
LOG_FILE="/var/log/floating-ip-monitor.log"

# Function to log messages
log_message() {
    echo "$(date): $1" >> "$LOG_FILE"
}

# Check if floating IP is configured
if ip addr show "$INTERFACE" | grep -q "$FLOATING_IP"; then
    log_message "Floating IP $FLOATING_IP is configured on $INTERFACE"
    
    # Test connectivity
    if ping -c 1 -W 5 "$FLOATING_IP" > /dev/null 2>&1; then
        log_message "Floating IP $FLOATING_IP is reachable"
        exit 0
    else
        log_message "WARNING: Floating IP $FLOATING_IP is not reachable"
        exit 1
    fi
else
    log_message "ERROR: Floating IP $FLOATING_IP is not configured"
    exit 2
fi

Automated Floating IP Assignment

#!/bin/bash
# assign-floating-ip.sh

FLOATING_IP="10.0.0.8"
INTERFACE="eth0"

# Check if IP is already assigned
if ! ip addr show "$INTERFACE" | grep -q "$FLOATING_IP"; then
    echo "Assigning floating IP $FLOATING_IP to $INTERFACE"
    
    # Add IP address
    sudo ip addr add "$FLOATING_IP/32" dev "$INTERFACE"
    
    # Add route
    sudo ip route add "$FLOATING_IP/32" dev "$INTERFACE"
    
    # Verify assignment
    if ip addr show "$INTERFACE" | grep -q "$FLOATING_IP"; then
        echo "Successfully assigned floating IP $FLOATING_IP"
    else
        echo "Failed to assign floating IP $FLOATING_IP"
        exit 1
    fi
else
    echo "Floating IP $FLOATING_IP is already assigned"
fi

Security Considerations

Implement security best practices when configuring floating IPs to protect your infrastructure.

Firewall Configuration for Floating IPs

# UFW firewall rules for floating IP
sudo ufw allow in on eth0 to 10.0.0.8 port 80
sudo ufw allow in on eth0 to 10.0.0.8 port 443
sudo ufw allow in on eth0 to 10.0.0.8 port 22

# iptables rules for floating IP
sudo iptables -A INPUT -d 10.0.0.8 -p tcp --dport 80 -j ACCEPT
sudo iptables -A INPUT -d 10.0.0.8 -p tcp --dport 443 -j ACCEPT
sudo iptables -A INPUT -d 10.0.0.8 -p tcp --dport 22 -j ACCEPT

# Save iptables rules
sudo iptables-save > /etc/iptables/rules.v4

Additional Resources for Network Management

• Official Netplan Documentation – Comprehensive Netplan configuration reference
• Ubuntu Network Configuration Guide – Ubuntu-specific networking documentation
• Debian Network Configuration – Debian networking setup and management
• Linux IP Command Manual – Complete reference for the ip command

Conclusion: Mastering Floating IP Configuration

Floating IP configuration using Netplan provides a robust foundation for high-availability infrastructure on Ubuntu and Debian systems. By understanding both persistent Netplan configurations and manual IP management techniques, you can implement reliable network failover solutions.

The combination of Netplan’s declarative configuration model and manual IP commands gives you flexibility for both permanent infrastructure and temporary testing scenarios. Whether you’re implementing load balancing, disaster recovery, or simple service migration, floating IPs provide the network agility needed for modern server management.

Ready to implement floating IPs in your infrastructure? Start with a test environment to familiarize yourself with Netplan configuration, then gradually deploy to production systems with proper monitoring and backup procedures in place.