Direct answer
For the Ubiquiti UniFi Cloud Gateway Ultra, local service, firewall, reserved IP, double NAT, CGNAT and provider blocks should be proved in order. First, verify the service locally and reserve its internal IP.
What this covers
- Ubiquiti UniFi Cloud Gateway Ultra (UCG-Ultra)
- UniFi network; Network application version, gateway ownership, VLANs, PoE and adoption state are part of every diagnosis.
- The specific fault this record addresses: port forwarding is not working
What it does not cover
- ×The same symptom on a different Ubiquiti product line, which has its own record and its own cited source
- ×An on-screen error code whose meaning has not been checked against this exact model's manual
- ×Live electrical, gas, sealed-system, internal battery-cell or structural repair — a technician boundary, not a self-service step
Differential
What actually causes this, and how to tell them apart
These are ordered by how often each one is the answer, not by how easy it is to try. The point of the middle column is that two causes producing the same headline symptom rarely produce the same detail — that detail is what tells you which one you have before you change anything.
- 1
The forwarding rule points at the wrong address or port
What separates it The rule exists but the service is unreachable from outside.
How to confirm Confirm the rule's internal IP matches the device's current address and the port/protocol matches the service; a device whose IP changed by DHCP breaks a rule pinned to the old address, so reserve its IP.
- 2
The internal service is not actually listening or is firewalled
What separates it The rule is correct but the device refuses the connection even on the local network.
How to confirm Test the service from inside the LAN first; if it fails locally, the forward is not the problem — the service or the device's own firewall is.
- 3
A double NAT is swallowing the forward
What separates it The rule is on your router but your router's WAN is a private address.
How to confirm Cross-check double NAT; with two NAT layers the forward has to exist on the outer router too, or the layers must be collapsed.
- 4
Carrier-grade NAT makes inbound forwarding impossible
What separates it Everything is correct but no inbound connection ever arrives, and the provider shares one public IP across many customers.
How to confirm Ask the provider whether the line is behind carrier-grade NAT; if so, no port forward can work without a public IP or the provider's own solution.
Before you touch a setting
Record this first — changing settings destroys the evidence
Every item below stops existing the moment a reset, re-pair or settings change is made. Written down first, they are what separates the causes above; recovered afterwards, they are guesswork.
- The rule's internal IP/port/protocol and whether the device's IP is reserved.
- Whether the service is reachable from inside the LAN at all.
- Your router's WAN IP — public, private (double NAT), or a shared carrier-grade range.
Verify the rule targets the device's current, reserved IP and correct port
ReversibleA DHCP address change silently breaks a rule pinned to the old one.
Confirm the service is listening by testing it from inside the LAN
ReversibleA service that fails locally will never work forwarded.
Check for a double NAT above your router
ReversibleA private WAN IP means the forward must exist on the outer router too.
Ask the provider about carrier-grade NAT if nothing inbound arrives
ReversibleCGNAT makes inbound forwarding impossible without a public IP.
Model-specific
What is true of this model and not of its siblings
Generic advice for the product line fails here. Each item below is a property of this specific model family that changes which of the steps above apply to you.
- Model scope
- UCG-Ultra. UniFi network; Network application version, gateway ownership, VLANs, PoE and adoption state are part of every diagnosis.
- Type — compact GATEWAY/router, NO Wi-Fi
- The UCG-Ultra is a small UniFi gateway (router, firewall, UniFi Network controller) with NO built-in Wi-Fi radio — it does not broadcast wireless. Wi-Fi symptoms do not apply; add separate UniFi APs. It is the compact, affordable way into the UniFi ecosystem.
- Needs separate access points
- 'No Wi-Fi' is expected — the Wi-Fi comes from UniFi APs connected to it (via a PoE switch/injector). Troubleshoot Wi-Fi at the APs.
- UniFi controller/app
- Runs the UniFi Network application on-device (managed web/app). Advanced compared with consumer routers.
- Symptom boundary
- This record covers Ubiquiti UniFi Cloud Gateway Ultra when it port forwarding is not working. A different symptom on the same hardware, or this symptom on a different Ubiquiti product line, has its own record with its own causes and its own cited source.
Stop boundary
When this stops being a self-service repair
Continuing past any one of these costs more than the repair saves — in safety, in warranty, or in evidence a technician needs.
- !Forward only the specific ports a service needs, never a wide range or the DMZ, and never expose an admin interface — an over-broad forward is a direct security hole.
Evidence ledger
Sources behind this answer
Visible sources support the visible claims. Home Product Support records the publisher, the fact used and the review date; community reports can suggest an issue but do not become a published fact on their own.
Where the manufacturer's article stops. Ubiquiti Help Center publishes this as "UniFi Gateway - Port Forwarding". Ubiquiti's own device-agnostic port-forwarding article. Verified reachable and content-matched via the Browser tool 2026-08-28. What that article does not carry is the model boundary — it is written for a product line, and UCG-Ultra is the scope applied here. Where a control label, terminal, indicator pattern or reset sequence differs on your unit, the manual for that exact model is the authority, not this page and not the article.
Exact questions
Common follow-ups
I set up a UniFi Cloud Gateway Ultra but have no Wi-Fi.+
That is because the Cloud Gateway Ultra has no built-in Wi-Fi radio — it is a compact gateway/router, not a wireless router. You need to add UniFi access points (such as a U6 Pro or U7 Pro), connect them (they need PoE, from a PoE switch or injector), and adopt them in the UniFi Network application running on the gateway. Once an AP is adopted and online, it broadcasts your Wi-Fi. The gateway itself only routes.
I set up port forwarding but it still doesn't work.+
Work through it in order. Confirm the rule points at the device's current IP (reserve that IP so DHCP cannot change it) and the right port and protocol. Then test the service from inside your own network — if it fails there, the forward is not the issue. Then check whether your router's WAN IP is private (a double NAT that also needs the rule on the outer router) or a shared carrier-grade address, which makes inbound forwarding impossible without the provider's help.
Does this answer apply to every Ubiquiti model?+
No. It is scoped to UCG-Ultra. UniFi network; Network application version, gateway ownership, VLANs, PoE and adoption state are part of every diagnosis.
What should I record before troubleshooting port forwarding or open port?+
Record the complete model identifier, exact message or indicator, software/firmware where visible, the operating stage and what still works.
Why is a factory reset not the first step?+
A reset can erase accounts, networks, maps, schedules or preferences without distinguishing port forwarding, open port. The ordered checks preserve that evidence.
When should I stop and use qualified service?+
Never expose insecure admin, camera or remote-desktop services.
Answer for the exact device and software version shown above.