DigitalOcean Reserved IPs (Floating IPs)

Overview

Reserved IPs (formerly called Floating IPs) are static IP addresses that can be instantly remapped between Droplets in the same datacenter. They provide high availability and enable seamless failover without DNS propagation delays.

Key Features

• Static IP Address: Permanent IP that persists independently of Droplets
• Instant Remapping: Switch between Droplets in seconds
• High Availability: Enable failover without DNS changes
• Regional Resource: Tied to a specific datacenter region
• Free When Assigned: No charge when assigned to a Droplet
• API Support: Automate failover and management
• Anchor Droplet: Can be assigned to one Droplet at a time

How Reserved IPs Work

┌─────────────────────────────────────────────────────────────┐
│                    Reserved IP Architecture                  │
└─────────────────────────────────────────────────────────────┘

                    Reserved IP: 203.0.113.10
                            │
                            │ (Assigned to)
                            │
                    ┌───────▼────────┐
                    │   Droplet 1    │
                    │   (Primary)    │
                    │  10.0.0.5      │
                    └────────────────┘

                    ─── Failover ───>

                    Reserved IP: 203.0.113.10
                            │
                            │ (Reassigned to)
                            │
                    ┌───────▼────────┐
                    │   Droplet 2    │
                    │   (Backup)     │
                    │  10.0.0.6      │
                    └────────────────┘

Reserved IP vs Regular IP

Feature	Reserved IP	Regular Droplet IP
Persistence	Independent of Droplet	Tied to Droplet lifecycle
Remapping	Instant between Droplets	Lost when Droplet destroyed
Failover	Seconds	Requires DNS change (minutes/hours)
Cost	$4/month when unassigned	Free with Droplet
Use Case	High availability	Standard deployments

Architecture Patterns

1. Active-Passive Failover

                        Internet
                            │
                            │
                    ┌───────▼────────┐
                    │  Reserved IP   │
                    │  203.0.113.10  │
                    └───────┬────────┘
                            │
                ┌───────────┴───────────┐
                │                       │
        ┌───────▼────────┐      ┌──────▼──────┐
        │  Primary Web   │      │ Backup Web  │
        │    Droplet     │      │   Droplet   │
        │   (Active)     │      │  (Standby)  │
        └───────┬────────┘      └──────┬──────┘
                │                       │
                └───────────┬───────────┘
                            │
                    ┌───────▼────────┐
                    │   Database     │
                    │    Cluster     │
                    └────────────────┘

Monitoring detects failure → Reassigns Reserved IP → Traffic flows to backup

2. Load Balancer with Reserved IP

                        Internet
                            │
                    ┌───────▼────────┐
                    │  Reserved IP   │
                    │  203.0.113.10  │
                    └───────┬────────┘
                            │
                    ┌───────▼────────┐
                    │ Load Balancer  │
                    │  (Primary)     │
                    └───────┬────────┘
                            │
        ┌───────────────────┼───────────────────┐
        │                   │                   │
   ┌────▼────┐         ┌────▼────┐        ┌────▼────┐
   │ Droplet │         │ Droplet │        │ Droplet │
   │  Web 1  │         │  Web 2  │        │  Web 3  │
   └─────────┘         └─────────┘        └─────────┘

3. Multi-Tier Application

                    Public Reserved IP
                      203.0.113.10
                            │
                    ┌───────▼────────┐
                    │   Web Tier     │
                    │   (Public)     │
                    └───────┬────────┘
                            │
                    Internal Reserved IP
                       10.0.0.100
                            │
                    ┌───────▼────────┐
                    │   App Tier     │
                    │   (Private)    │
                    └───────┬────────┘
                            │
                    Internal Reserved IP
                       10.0.0.200
                            │
                    ┌───────▼────────┐
                    │   DB Tier      │
                    │   (Private)    │
                    └────────────────┘

Creating and Managing Reserved IPs

Via Control Panel

1. Create Reserved IP
2. Navigate to Networking → Reserved IPs
3. Click Create Reserved IP
4. Select region (must match Droplet region)
5. Choose Droplet to assign (optional)

6. Click Create

7. Assign to Droplet

8. Select Reserved IP
9. Click Assign to Droplet
10. Choose target Droplet

11. Confirm assignment

12. Reassign to Different Droplet

13. Select Reserved IP
14. Click Reassign
15. Choose new Droplet
16. Confirm (takes 5-10 seconds)

Via API

Create Reserved IP

curl -X POST \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $DIGITALOCEAN_TOKEN" \
  -d '{"type":"assign","droplet_id":12345678,"region":"nyc3"}' \
  "https://api.digitalocean.com/v2/floating_ips"

List Reserved IPs

curl -X GET \
  -H "Authorization: Bearer $DIGITALOCEAN_TOKEN" \
  "https://api.digitalocean.com/v2/floating_ips"

Assign to Droplet

curl -X POST \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $DIGITALOCEAN_TOKEN" \
  -d '{"type":"assign","droplet_id":87654321}' \
  "https://api.digitalocean.com/v2/floating_ips/203.0.113.10/actions"

Unassign from Droplet

curl -X POST \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $DIGITALOCEAN_TOKEN" \
  -d '{"type":"unassign"}' \
  "https://api.digitalocean.com/v2/floating_ips/203.0.113.10/actions"

Delete Reserved IP

curl -X DELETE \
  -H "Authorization: Bearer $DIGITALOCEAN_TOKEN" \
  "https://api.digitalocean.com/v2/floating_ips/203.0.113.10"

Via doctl CLI

# Create and assign Reserved IP
doctl compute floating-ip create --region nyc3 --droplet-id 12345678

# List Reserved IPs
doctl compute floating-ip list

# Assign to Droplet
doctl compute floating-ip-action assign 203.0.113.10 --droplet-id 87654321

# Unassign from Droplet
doctl compute floating-ip-action unassign 203.0.113.10

# Delete Reserved IP
doctl compute floating-ip delete 203.0.113.10

Configuring Reserved IP on Droplet

Automatic Configuration (Recommended)

DigitalOcean automatically configures Reserved IPs via cloud-init on supported images. No manual configuration needed.

Manual Configuration (Ubuntu/Debian)

If automatic configuration fails, configure manually:

# Edit network configuration
sudo nano /etc/network/interfaces.d/60-floating-ip.cfg

# Add configuration
auto eth0:1
iface eth0:1 inet static
    address 203.0.113.10
    netmask 255.255.255.255

# Restart networking
sudo systemctl restart networking

# Verify
ip addr show eth0

Manual Configuration (CentOS/RHEL)

# Create network script
sudo nano /etc/sysconfig/network-scripts/ifcfg-eth0:1

# Add configuration
DEVICE=eth0:1
BOOTPROTO=static
IPADDR=203.0.113.10
NETMASK=255.255.255.255
ONBOOT=yes

# Restart networking
sudo systemctl restart network

# Verify
ip addr show eth0

Automated Failover Implementation

Using Heartbeat

# Install heartbeat on both Droplets
sudo apt-get update
sudo apt-get install heartbeat

# Configure /etc/ha.d/ha.cf
debugfile /var/log/ha-debug
logfile /var/log/ha-log
logfacility local0
keepalive 2
deadtime 30
warntime 10
initdead 120
udpport 694
ucast eth0 10.0.0.6  # IP of other node
auto_failback on
node primary-droplet
node backup-droplet

# Configure /etc/ha.d/haresources
primary-droplet IPaddr::203.0.113.10/32/eth0:1

# Configure /etc/ha.d/authkeys
auth 1
1 sha1 your-secret-key-here

# Set permissions
sudo chmod 600 /etc/ha.d/authkeys

# Start heartbeat
sudo systemctl start heartbeat
sudo systemctl enable heartbeat

Using Custom Script with API

#!/usr/bin/env python3
import requests
import time
import subprocess

DIGITALOCEAN_TOKEN = "your_token_here"
RESERVED_IP = "203.0.113.10"
BACKUP_DROPLET_ID = "87654321"
CHECK_INTERVAL = 30  # seconds

def check_primary_health():
    """Check if primary service is healthy"""
    try:
        response = subprocess.run(
            ["curl", "-f", "http://localhost/health"],
            capture_output=True,
            timeout=5
        )
        return response.returncode == 0
    except:
        return False

def reassign_reserved_ip():
    """Reassign Reserved IP to backup Droplet"""
    url = f"https://api.digitalocean.com/v2/floating_ips/{RESERVED_IP}/actions"
    headers = {
        "Authorization": f"Bearer {DIGITALOCEAN_TOKEN}",
        "Content-Type": "application/json"
    }
    data = {
        "type": "assign",
        "droplet_id": BACKUP_DROPLET_ID
    }

    response = requests.post(url, headers=headers, json=data)
    return response.status_code == 201

def main():
    consecutive_failures = 0

    while True:
        if check_primary_health():
            consecutive_failures = 0
        else:
            consecutive_failures += 1

            if consecutive_failures >= 3:
                print("Primary failed 3 times, initiating failover...")
                if reassign_reserved_ip():
                    print("Failover successful!")
                    break
                else:
                    print("Failover failed, retrying...")

        time.sleep(CHECK_INTERVAL)

if __name__ == "__main__":
    main()

High Availability Workflow

┌─────────────────────────────────────────────────────────────┐
│              High Availability Workflow                      │
└─────────────────────────────────────────────────────────────┘

1. Normal Operation
   ├─> Reserved IP assigned to Primary Droplet
   ├─> Monitoring checks health every 30s
   └─> All traffic flows to Primary

2. Failure Detection
   ├─> Health check fails on Primary
   ├─> Wait for 3 consecutive failures (90s)
   └─> Trigger failover process

3. Failover Execution
   ├─> API call to reassign Reserved IP
   ├─> Reserved IP moves to Backup Droplet
   ├─> Takes 5-10 seconds to complete
   └─> DNS remains unchanged

4. Traffic Restoration
   ├─> New connections go to Backup
   ├─> Existing connections may drop
   ├─> Service restored in < 2 minutes
   └─> Alert administrators

5. Recovery
   ├─> Fix Primary Droplet
   ├─> Verify health
   ├─> Optional: Failback to Primary
   └─> Resume normal monitoring

Use Cases

1. Web Application High Availability

• Assign Reserved IP to primary web server
• Monitor application health
• Automatic failover to backup server
• Zero DNS propagation delay

2. Database Failover

• Reserved IP for database master
• Standby replica ready for promotion
• Quick failover during maintenance or failure
• Applications reconnect automatically

3. API Gateway

• Reserved IP for API endpoint
• Multiple backend servers
• Seamless version upgrades
• Blue-green deployments

4. Email Server

• Reserved IP with PTR record
• Maintain sender reputation
• Failover without affecting deliverability
• Consistent IP for SPF records

Best Practices

1. Regional Planning
2. Reserved IPs are regional resources
3. Plan Droplet placement in same region

4. Consider multi-region for disaster recovery

5. Monitoring

6. Implement robust health checks
7. Monitor both application and infrastructure
8. Set up alerting for failover events

9. Log all IP reassignments

10. Testing

11. Regularly test failover procedures
12. Verify backup Droplet readiness
13. Measure failover time

14. Document recovery procedures

15. DNS Configuration

16. Point DNS A records to Reserved IP
17. Use appropriate TTL values
18. Configure PTR records if needed

19. Document DNS setup

20. Security

21. Protect API tokens
22. Use Cloud Firewalls with Reserved IPs
23. Implement rate limiting

24. Monitor for unauthorized access

25. Cost Management

26. Always assign Reserved IPs to avoid charges
27. Delete unused Reserved IPs
28. Monitor billing for unassigned IPs
29. Plan capacity appropriately

Limitations

• Regional Scope: Cannot move between regions
• One Droplet: Can only be assigned to one Droplet at a time
• Same Region: Droplet must be in same region as Reserved IP
• IPv4 Only: No IPv6 Reserved IPs currently
• Charge When Unassigned: $4/month if not assigned to a Droplet

Troubleshooting

Reserved IP Not Responding

# Check if IP is assigned
doctl compute floating-ip list

# Verify Droplet configuration
ip addr show

# Check firewall rules
sudo iptables -L -n

# Test connectivity
ping 203.0.113.10
curl -I http://203.0.113.10

Failover Not Working

1. Verify API token permissions
2. Check Droplet is in same region
3. Ensure Droplet is powered on
4. Review API rate limits
5. Check monitoring script logs

Configuration Issues

# Verify network configuration
ip addr show eth0

# Check routing
ip route show

# Test local binding
netstat -tulpn | grep 203.0.113.10

# Restart networking
sudo systemctl restart networking

Pricing

• Assigned to Droplet: Free
• Unassigned: $4.00/month
• No Data Transfer Charges: Standard Droplet bandwidth applies

Related Services

• Domains & DNS - Point DNS to Reserved IPs
• Load Balancers - Combine for advanced HA
• Cloud Firewalls - Secure Reserved IPs
• PTR Records - Reverse DNS for Reserved IPs