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DDNS for Synology NAS: Setup & Troubleshooting Guide

DDNS for Synology NAS: Complete Setup & Troubleshooting Guide

Dynamic DNS (DDNS) is an essential feature for Synology NAS users who need secure and reliable remote access. Since most internet connections use dynamic IP addresses that change periodically, DDNS ensures you can always reach your NAS using a consistent hostname even when your public IP changes.

This guide explains what DDNS is, how to set it up on a Synology NAS, common issues users face, and practical troubleshooting steps. Whether you’re accessing files remotely, managing backups, or supporting remote teams, a properly configured DDNS setup is critical for stability and security.

What Is DDNS and Why Does It Matter for Synology NAS

DDNS maps a changing public IP address to a fixed domain name (for example, yourname.synology.me). When your ISP updates your IP address, the DDNS service automatically updates the DNS record, so users don’t need to know the new IP.

For Synology NAS users, DDNS enables:

  • Secure remote access to DSM.

  • Offsite file sharing and collaboration

  • Remote backup replication

  • VPN and application access without a static IP costs

Without DDNS, every IP change would require manual reconfiguration, creating downtime and access failures.

How to Set Up DDNS on Synology NAS

Setting up DDNS on Synology NAS is straightforward and built directly into DiskStation Manager (DSM).

Step 1: Open External Access Settings

  1. Log in to DSM

  2. Go to Control Panel → External Access → DDNS.

  3. Click Add

Step 2: Choose a DDNS Provider

Synology supports:

  • Synology DDNS (free, recommended)

  • Third-party providers (No-IP, DynDNS, others)

Select Synology if you want a simple, no-cost option tightly integrated with DSM.

Step 3: Configure Hostname and Credentials

  • Enter your desired hostname.

  • Provide your Synology Account (or third-party credentials)

  • Confirm your external IP and network interface

DSM will automatically test the connection and confirm status.

Step 4: Apply and Verify

Once enabled, the status should show “Normal”. You can test by accessing your NAS externally using the DDNS hostname.

Common DDNS Issues and How to Fix Them

Even with a correct setup, DDNS can fail due to network or configuration problems.

1. DDNS Status Shows “Failed” or “Updating.”

Possible causes:

  • Incorrect credentials

  • DNS resolution issues

  • Firewall blocking outbound traffic.

Fix:
Re-enter credentials, verify DNS settings, and ensure outbound ports (80/443) are allowed.

2. DDNS Works Internally but Not Externally

This usually indicates a router or NAT issue.

Fix:

  • Confirm port forwarding is configured correctly.

  • Ensure the NAS has a static local IP

  • Disable double NAT if using multiple routers

3. ISP Blocking Ports or CGNAT

Some ISPs block common ports or use Carrier-Grade NAT (CGNAT), preventing inbound access.

Fix:

  • Change DSM ports

  • Use Synology QuickConnect as a fallback.

  • Consider VPN-based access instead of direct exposure.

4. SSL Certificate Errors

DDNS hostnames require valid SSL certificates for secure access.

Fix:

  • Request a Let’s Encrypt certificate inside DSM.

  • Assign the certificate to DSM and relevant services

Security Best Practices for DDNS Access

DDNS enables convenience, but security must come first.

Recommended practices:

  • Enable two-factor authentication (2FA)

  • Restrict DSM access by IP or country.

  • Use custom ports instead of defaults.

  • Enable Synology firewall rules.

  • Log and monitor login attempts.

DDNS should never expose an unprotected admin interface to the public internet.

Synology-Focused Solution Overview

Synology provides a fully integrated DDNS solution within DSM, eliminating the need for manual scripts or external clients. Combined with DSM’s firewall, auto-blocking, certificate management, and VPN tools, Synology allows administrators to build secure remote-access architectures without relying solely on open ports. For many environments, DDNS paired with VPN or reverse proxy features offers a strong balance between accessibility and security, especially when managing distributed users or remote offices.

How Epis Technology Supports Secure DDNS Deployments

While Synology’s DDNS tools are powerful, improper configuration can expose systems to unnecessary risk. Epis Technology helps businesses design and deploy secure remote-access strategies using Synology NAS. The team evaluates network topology, ISP limitations, firewall rules, and compliance requirements before implementing DDNS, VPN, or hybrid-access models. Epis Technology also assists with SSL certificate management, intrusion prevention, and monitoring, ensuring remote access is reliable, secure, and aligned with business continuity goals.

Best Practices Checklist for Synology DDNS

  • Assign a static LAN IP to the NAS.

  • Enable HTTPS and valid SSL certificates.

  • Use firewall rules and IP restrictions.

  • Avoid exposing DSM admin ports directly.

  • Monitor logs and update DSM regularly.

Following these steps reduces downtime and security risks.

DDNS is a powerful feature that makes Synology NAS accessible from anywhere, but only when configured correctly. By understanding setup steps, common issues, and security considerations, users can avoid most DDNS-related problems.

With Synology’s built-in tools and expert support from Epis Technology, organizations can achieve secure, stable, and scalable remote access without the complexity or cost of static IP addresses.

About Epis Technology

Epis Technology provides enterprise IT infrastructure, Synology consulting, and data protection services. The company specializes in secure NAS deployment, hybrid cloud integration, Microsoft 365 and Google Workspace backups, large storage systems, and business continuity planning. Epis Technology helps organizations design, secure, and optimize their Synology environments for long-term reliability and growth.

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