Prerequisites for Custom Domain Setup
Before attempting to configure the Dynamic DNS service on your Synology NAS, you need to prepare several external components. The most critical requirement is ownership of a domain name. You cannot use a generic synology.me address if you wish to have a custom sub-domain like nas.yourdomain.com. You must purchase a domain from a registrar such as GoDaddy, Namecheap, Cloudflare, or any other provider that offers dynamic DNS update capabilities.
Additionally, your internet service provider (ISP) must allow incoming connections on standard ports, typically port 80 for HTTP and port 443 for HTTPS. Some residential ISPs block these ports to prevent hosting servers. If your ISP blocks these ports, you will need to either contact them to request unblocking or use alternative methods like port forwarding through a different gateway, though this guide assumes standard port accessibility. Ensure that your router’s WAN IP address is static or that your ISP provides a consistent public IP, as DDNS relies on tracking changes to this IP address.
You also need to identify which DNS provider your domain uses. Not all providers support the protocol required by Synology’s built-in DDNS client. Most major providers do, but it is essential to verify compatibility. For example, Cloudflare requires an API token, while older registrars might only support username and password authentication. Gather these credentials before logging into your NAS interface to streamline the configuration process.
Accessing Synology NAS via DDNS Url with HAproxy through pFsense provides additional context on how DDNS integrates with broader network security architectures, which may be relevant if you are planning advanced routing configurations later.Creating the Sub-Domain Record
The first technical step involves creating the actual sub-domain entry in your DNS provider’s management console. Log in to your domain registrar or DNS host website. Navigate to the DNS Management or Zone Editor section for your specific domain. Look for an option to add a new record. You will typically choose an "A" record, which maps a hostname directly to an IPv4 address.
- Host/Name: Enter the desired sub-domain prefix. For example, if your domain is
example.comand you wantnas.example.com, enternas. - Type: Select "A" for IPv4 addresses. If you are using IPv6 exclusively, select "AAAA", though IPv4 remains the standard for most home NAS setups.
- Value/Content: You can temporarily enter your current public IP address, or leave it blank if the provider allows null records that will be updated dynamically. It is often safer to enter your current IP initially to verify connectivity.
- TTL (Time To Live): Set this to the lowest possible value, such as 1 minute or 300 seconds. This ensures that when your IP changes, the DNS propagation happens quickly, reducing downtime.
After saving the record, verify that the sub-domain resolves correctly by using a command-line tool like ping nas.yourdomain.com from a computer outside your local network. This confirms that the DNS record exists and is pointing to the correct location before you attempt to automate the updates from your NAS.
Configuring DDNS in DSM
With the DNS record created, log in to your Synology NAS via its local IP address and open the Control Panel. Navigate to External Access and then click on the DDNS tab. You will see a list of currently configured services, including the default Synology DDNS if previously set up.
- Click the Create button to add a new service.
- In the Service Name dropdown, scroll down and select the provider corresponding to your domain registrar. If your provider is not listed, you may need to select "Custom" and input the update URL manually, which is less common for modern providers.
- Enter the full hostname, e.g.,
nas.yourdomain.com. - Provide the Username and Password required by your DNS provider. For API-based providers like Cloudflare, the "Username" field might require your account email and the "Password" field might require the API token.
- Check the box to Enable Remote Connection if you want the NAS to automatically adjust firewall rules, though this is optional depending on your router setup.
Once the fields are populated, click Test Connection. If successful, the system will display a confirmation message. Click Save to store the configuration. The NAS will now periodically check your public IP address and send update requests to your DNS provider whenever a change is detected.
Directly Save Video Camera Feed from Linux Machine to Synology NAS via SSH highlights another use case where reliable remote access via DDNS is crucial for integrating external devices with your storage infrastructure.Troubleshooting Common Issues
If the connection test fails, the most frequent cause is incorrect authentication credentials. Double-check that your API key or password has not expired or been rotated. Another common issue is DNS propagation delay. After changing the sub-domain record, it may take several minutes to hours for the change to reflect globally. Use online DNS lookup tools to verify the status.
Ensure that your router’s port forwarding is correctly configured to direct traffic from port 80 and 443 to the local IP address of your Synology NAS. Without proper port forwarding, even a working DDNS service will result in connection timeouts when accessed from outside your home network. Additionally, verify that no firewall on the NAS itself is blocking inbound connections on these ports by checking the Firewall rule settings in the Control Panel.
Frequently Asked Questions
Can I use the same domain for multiple NAS devices?
Yes, you can create multiple sub-domains under the same domain, such as nas1.yourdomain.com and nas2.yourdomain.com. Each sub-domain requires a separate A record in your DNS provider’s console and a distinct DDNS configuration entry within the Synology DSM interface. This allows you to manage different services or locations independently while sharing a single domain registration.
Why does my DDNS connection fail after my ISP restarts my modem?
This usually occurs because your ISP assigns a new dynamic IP address upon reboot. The Synology NAS detects this change and attempts to update the DNS record. If the update fails, check your provider credentials again. Sometimes, the ISP may assign a private IP address behind CGNAT, which prevents external access entirely. In such cases, DDNS alone is insufficient, and you may need to request a static public IP from your ISP or use a tunneling service.
Is it safe to expose my NAS to the internet using DDNS?
Exposing your NAS directly carries risks if proper security measures are not in place. Always enable two-factor authentication (2FA) for your DSM admin account, disable the default admin user, and keep your DSM firmware updated. Consider using reverse proxies or VPNs instead of direct exposure for sensitive data. DDNS facilitates access but does not encrypt or secure the connection by itself; you must implement these protections separately.
How often does Synology update the IP address?
Synology NAS devices typically check for IP address changes every few minutes, often around every 5 to 10 minutes, depending on the DSM version and load. When a change is detected, an immediate update is sent to the DNS provider. This frequency balances the need for timely updates with the risk of being rate-limited by the DNS provider. You generally do not need to adjust this interval manually.
What should I do if my DNS provider is not listed in DSM?
If your provider is not in the default list, you can select the "Custom" option in the Service Name dropdown. You will need to find the specific URL endpoint used by your provider for dynamic DNS updates. This URL usually requires placeholders for the username, password, and hostname. Consult your DNS provider’s documentation for the exact API endpoint format to ensure the NAS can communicate with their servers successfully.