The UniFi Cloud Gateway Ultra has a 2.5 Gigabit WAN port and Gigabit LAN ports, and a wired connection that is slower than the plan has a short list of causes that the UniFi community has worked through. The first is the threat-management feature. Intrusion detection and prevention inspects every packet, and the Ultra's own specification lists a throughput for that mode of about 1 Gbps, so a household with a faster plan sees the cap as soon as the feature is switched on, which the ShiftCtrl article on UniFi threat management describes in detail.
The checks in more detail
Test by turning IDS/IPS off in Settings, Security, and running a speed test from a wired computer; if the figure rises to the plan, the feature is the limit and you can choose the protection level you want. The second cause is the link speed of the port: open the device's port view in the UniFi application and check that the WAN is linked at 2.5 Gbps and the LAN port at 1 Gbps, and swap a cable that negotiates at 100 Mbps, since a damaged cable or a bad connector drops the link down to a slow speed.
The third cause is hardware limits. The LAN ports are Gigabit, so a single wired computer cannot exceed about 940 Mbps whatever the plan, and the 2.5 Gbps WAN helps only for a larger plan shared among several devices. Some owners report that the 2.5 Gbps WAN under real routed traffic gives less than the internal speed test suggests, and that a firmware update or setting the WAN to 1 Gbps stabilized it, so check for a new UniFi OS release and try forcing the link speed as a test.
Test with a computer plugged directly into the modem or ONT to learn what the provider delivers, then through the gateway. Check smart queues, which limit throughput when set to a lower value than the plan; switch them off for a test. Look at the switch or cable between the gateway and your device, since a cheap switch or a long old cable limits the speed. Keep the application and gateway firmware current. If the figures fall far below the plan with threat management off, smart queues off and good cables, contact Ubiquiti support with the speed test and the port statistics.
Differential
Likely causes of “Ubiquiti UniFi Cloud Gateway Ultra Ethernet link is limited to 100 Mbps or disconnects”, and how to tell them apart
- 1
Threat management on
What separates it Speed caps near 1 Gbps
How to confirm Test with IDS/IPS off and choose the level you need
- 2
A cable or port at a low link speed
What separates it The port shows 100 Mbps
How to confirm Replace the cable
- 3
The Gigabit LAN limit
What separates it A wired device never exceeds about 940 Mbps
How to confirm Expect that ceiling, use several devices for more
- 4
Smart queues set too low
What separates it Speed limited by a setting
How to confirm Turn them off for a test
- 5
A firmware or WAN behavior
What separates it Less than the speed test suggests
How to confirm Update and try a 1 Gbps WAN link as a test
Before you touch a setting
Record this first — changing settings destroys the evidence
- The speed with threat management on and off
- The port link speeds
- The plan speed
- The firmware version
Try in this order
0 of 6 completedRun a wired speed test
ReversibleNote the figure.
Turn off IDS/IPS
ReversibleAnd test again.
Check port link speeds
ReversibleIn the UniFi application.
Replace the cable
ReversibleIf it negotiates low.
Turn off smart queues
ReversibleFor a test.
Update the gateway
ReversibleTo the latest.
Model-specific
What is true of this model and not of its siblings
- IDS/IPS ceiling
- About 1 Gbps on this model.
- Gigabit LAN
- Each LAN port tops out near 940 Mbps.
Stop boundary
When this stops being a self-service repair
- !If speeds stay low with threat management and smart queues off, contact Ubiquiti with port statistics
- !If the modem direct test is slow, contact the provider
- !Update UniFi OS
Evidence ledger
Sources behind this answer
Ports, routing and IDS/IPS throughput of the Cloud Gateway Ultra.
Owners comparing throughput with and without threat management.
How IDS/IPS caps WAN throughput on UniFi gateways.
A review of the Cloud Gateway Ultra's routing ceiling.
Exact questions
Common questions
Why is my Cloud Gateway Ultra slow?+
IDS/IPS caps throughput near 1 Gbps.
What is the WAN speed?+
2.5 Gbps.
Can one wired device exceed 1 Gbps?+
Not on the Gigabit LAN ports.
Should I disable threat management?+
Only to test.