A wired connection through the UniFi Dream Machine SE that runs slower than it should is usually held back by a cable, a port speed that has negotiated down, an internet plan limit or the gateway's own features, and a few measurements separate them. The UDM SE has eight gigabit ports, one 2.5 gigabit port and two 10 gigabit SFP+ ports, so first work out which port the device uses and what speed it expects. In the UniFi Network app, open the device's port view or Devices, choose the UDM SE and look at each port's negotiated speed.
The checks in more detail
A gigabit port that shows 100 megabits has a poor cable, a damaged connector or a device that is set to a lower speed. Replace the cable with a good Cat 5e or Cat 6 cable and check the result. Then separate the local network from the internet. Test a file copy between two local wired devices, or run an iperf test; if that is fast, the local network is fine and the limit is the internet plan, the modem or the gateway's routing performance.
Test the internet speed from a wired computer connected to the gateway, and compare it to the plan. If it is slow only on the internet, check the modem and the provider. Intrusion detection and prevention can slow the throughput of a gateway when many rules are on, as can deep packet inspection and some traffic rules, so for a test turn off IDS and IPS and run the test again. Look for other limits. Smart queues, which shape traffic to avoid bufferbloat, limit speed to the rate you set; if the rate is set too low, the connection will be slow, so check it matches your plan.
Check whether the traffic goes through the gateway's routing or is switched locally between ports on the same network, which is faster. A slow link from one device only may point to its network card or driver. Update the firmware, and restart the unit. For 2.5 gigabit or 10 gigabit devices, check that the cable supports the speed and the ports are set to auto. If speeds remain low with a good cable and features off, ask Ubiquiti support or the community with the test results and logs.
Differential
Likely causes of “Ubiquiti UniFi Dream Machine Special Edition Ethernet link is limited”, and how to tell them apart
- 1
A poor cable or damaged connector
What separates it The port negotiates at a lower speed
How to confirm Replace the cable
- 2
IDS, IPS or deep packet inspection
What separates it Internet throughput is lower than the plan
How to confirm Test with them off and tune the rules
- 3
A smart queue rate set too low
What separates it Speed is capped
How to confirm Set it to match the plan
- 4
The provider or modem
What separates it A wired computer is slow to the internet
How to confirm Check the modem and contact the provider
- 5
A device's network card or driver
What separates it One device is slow
How to confirm Test another device
Before you touch a setting
Record this first — changing settings destroys the evidence
- The negotiated port speed
- A local transfer speed
- The internet speed from a wired computer
- Whether IDS or IPS is on
Try in this order
0 of 6 completedCheck the port speed
ReversibleIn the UniFi Network app.
Replace the cable
ReversibleWith Cat 5e or Cat 6.
Test a local transfer
ReversibleTo separate local from internet.
Test with IDS and IPS off
ReversibleThen back on.
Check the smart queue rate
ReversibleAgainst the plan.
Update the firmware
ReversibleAnd restart.
Model-specific
What is true of this model and not of its siblings
- Port speeds
- Eight gigabit, one 2.5 gigabit, two 10 gigabit SFP+.
- IPS
- It uses processing power.
Stop boundary
When this stops being a self-service repair
- !If speeds stay low with a good cable and features off, ask Ubiquiti with the results and logs
- !Contact the provider if the modem is slow
- !Turn IPS back on after testing
Evidence ledger
Sources behind this answer
Exact questions
Common questions
Why is my wired speed slow?+
A cable, IDS or IPS, or a rate limit.
What speed should the port show?+
Gigabit or more, not 100 megabits.
Does IPS slow it?+
With many rules, it can.
Should I test locally?+
Yes, it separates the causes.