FAQ
TL;DR: Fix “can’t reach Zyxel NSA310 from the internet” by avoiding double NAT, forwarding the right ports, and running DDNS on the main router. Statistic: upload under 20 Mb will feel slow; “If you have less than 20Mb on uploading…it will be a pain.” [Elektroda, KOCUREK1970, post #18098344]
Why it matters: This FAQ helps home users make Zyxel NSA310 reachable from outside networks without breaking local Wi‑Fi or security.
Quick Facts
- Use a public (not private/CGNAT) IP; otherwise inbound access will fail. [Elektroda, KOCUREK1970, post #16762609]
- Configure DDNS (e.g., No‑IP) on the main router; you can also enable it on the NAS. [Elektroda, sosarek, post #16761810]
- Two routers create double NAT; either forward on both or bridge the first. [Elektroda, kadzislaw, post #16761823]
- UPC modems lack NAT loopback; domains won’t open from LAN—test via mobile data. [Elektroda, KOCUREK1970, post #18098262]
- Common Zyxel access ports: 80/8080/8081 (HTTP/UI) or FTP as configured. [Elektroda, kadzislaw, post #16761823]
How do I fix “Zyxel NSA310 not reachable from the internet” with Dasan H660GW + TP‑LINK Archer D5?
Eliminate double NAT or forward traffic across both routers. Put DDNS on the main router (Dasan). Forward required ports on Dasan to TP‑LINK, then from TP‑LINK to the Zyxel’s static LAN IP. Confirm you have a public IP. Test from an external network, not your home Wi‑Fi. [Elektroda, sosarek, post #16761810]
Which device should run No‑IP (DDNS): router or Zyxel?
Run DDNS on the main, internet‑facing router so the hostname always tracks your WAN IP. You can also enable DDNS on Zyxel as a backup, but the upstream router remains the source of truth for the WAN address. [Elektroda, sosarek, post #16761810]
Do I need a public IP from my ISP for external access?
Yes. Without a public IP, inbound connections cannot reach your network. Ask your ISP to provide a public or static IP if you’re behind CGNAT or a private address. Verify in the router status page and with an external IP checker. [Elektroda, KOCUREK1970, post #16762609]
What is double NAT, and why does it break access?
Double NAT occurs when two routers each translate addresses. Your TP‑LINK sits behind the Dasan, so inbound traffic stops unless you chain port forwards or bridge one device. Symptom: services work on LAN but fail from outside. [Elektroda, kadzislaw, post #16761823]
Which ports should I forward for Zyxel NSA310?
Forward the web UI port you use (commonly 80/8080/8081) and any service ports you enable (e.g., FTP). Point each forward at the Zyxel’s fixed LAN IP. Avoid exposing admin UI broadly; restrict or use a VPN when possible. [Elektroda, kadzislaw, post #16761823]
How do I set up port forwarding on TP‑LINK Archer D5?
Use a simple 3‑step flow: 1. Reserve a static IP for the NAS. 2. Add a Virtual Server entry for the chosen port to the NAS IP. 3. Repeat on the upstream router to the TP‑LINK’s WAN IP. [Elektroda, Przemek52o, post #16761831]
I’m on UPC. Why does my No‑IP domain fail only inside my home?
UPC modems lack NAT loopback. Hostnames that resolve to your public IP won’t connect from your LAN. Test from mobile data or another network, or connect by the NAS’s local IP while at home. “NAT Loopback is not supported on UPC modemorouters.” [Elektroda, KOCUREK1970, post #18098262]
What is NAT loopback in plain English?
It lets you reach your public hostname from inside the same LAN. Without it, your domain looks out to the internet and cannot hairpin back in. Many ISP‑supplied routers omit this, so LAN tests fail while the service works externally. [Elektroda, KOCUREK1970, post #18098262]
Should I disable DHCP on the secondary router?
If the NAS sits behind a second router acting as an access point, disabling its DHCP avoids IP conflicts and simplifies routing. Then only the main router assigns addresses, reducing misroutes during port forwarding. [Elektroda, Przemek52o, post #16761814]
How do I map the NAS as a drive locally vs over the internet?
Map drives on LAN using your NAS’s local IP or hostname. For internet access, you don’t need NAT loopback; connect via public IP or DDNS name. Use SMB/VPN for security, or FTP/SFTP when necessary. [Elektroda, KOCUREK1970, post #18098307]
Is my upload speed really that important for remote access?
Yes. Your upload sets the ceiling for remote download. Expect sluggish transfers below 20 Mb upload. Quote: “If you have less than 20Mb on uploading… it will be a pain.” Plan services accordingly or upgrade. [Elektroda, KOCUREK1970, post #18098344]
Why can’t I reach the NAS even though DDNS says Success?
DDNS only updates the hostname. You must still forward ports through every NAT layer and ensure the ISP gives you a reachable public IP. Also verify you’re testing from an external network, not the LAN without loopback. [Elektroda, kadzislaw, post #16761805]
Can I run FTP without a router at all?
Yes, if you connect the NAS directly to one computer, FTP will work only for that machine. This bypasses routing but removes multi‑device access until you rejoin the LAN. [Elektroda, KOCUREK1970, post #18098307]
Do I need to touch both routers or only TP‑LINK?
With Dasan upstream and TP‑LINK downstream, configure both unless you bridge one. Forward on Dasan to TP‑LINK’s WAN IP, then on TP‑LINK to the NAS. Skipping the first hop leaves inbound traffic blocked. [Elektroda, kadzislaw, post #16761823]
Why do HTTP ports 80/8080/8081 matter on Zyxel?
Zyxel’s web services commonly listen on these ports. Forward only the one you use, and change it if your ISP blocks 80. Document the choice so DDNS tests the correct endpoint later. [Elektroda, kadzislaw, post #16761823]
I got a fixed IP, but access still fails. What’s the edge case?
Static IP helps, but forwarding must still cross all NAT layers. One missed hop or a disabled service on the NAS causes failure. Validate each hop with a port‑check tool and test externally to confirm reachability. [Elektroda, kadzislaw, post #16762732]
